Bulletin of the American Physical Society
65th Annual Meeting of the APS Division of Fluid Dynamics
Volume 57, Number 17
Sunday–Tuesday, November 18–20, 2012; San Diego, California
Session F1: Poster Session (5:50PM6:50PM) 
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Chair: Juan Carlos del Alamo, University of California, San Diego Room: Ballroom 20D Foyer 

F1.00001: MICROFLUIDICS 

F1.00002: Film thickness between a bubble and the inner wall of vertical tubes containing viscous liquids Guadalupe Gutierrez, Abel LopezVilla, Abraham Medina We study numerically the film thickness in between the free surface of a bubble and the inner wall in a vertical tube filled with a viscous liquid. The computations were performed using the Boundary element method to solve the Stokes equations and a fourth order RungeKutta scheme to build the bubble shape. After the computation of the bubble shape, the thickness of the annular film was calculated for low Bond numbers and a wide range of Capillary numbers, Ca. For the case Ca close to zero (inviscid approximation) it is found that the film actually touches the wall, meanwhile for the viscous cases always there is a film of finite thickness. [Preview Abstract] 

F1.00003: Selfintroduced thermocapillary convection in the evaporating process of a suspending drop JingChang Xie We studied the evaporation process of an evaporating ethanol drop coupled with selfintroduced thermocapillary convection. The drop was suspended on the bottom of a rod to reduce the effect of buoyancy. We used different particle tracers to visualize the interior flow field and the gaseous exterior of the drop and measured the temperature distributions inside and outside the evaporating drop. Both good heat conductor and heat insulating material were used as the rod materials to investigate their effects on the surface temperature distribution of an evaporating drop. In the case of a copper rod with ethanol drop in ambient temperature, temperature gradient existed on the drop surface which results in a stable thermocapillary convection and cells appeared near the surface in the drop throughout entire evaporating process. The convection greatly changed the temperature distribution and the way energy and mass transfer. Temperature discontinuity was found existing at the surface of the evaporating drop. The boundary condition at the surface of the evaporating drop can lead to gaseous exterior convective transport. Because of the existence of thermocapillary convection, drop evaporating process or evaporating rate is enhanced. [Preview Abstract] 

F1.00004: HoleClosing of a Surfactant Layer on a Thin Fluid Film Matthew Hin, M. Richard Sayanagi, Rachel Levy, Karen Daniels The spreading of surfactants on a thin fluid layer has been most commonly studied in an outwardspreading geometry. We report experiments on the inverse, the inward spreading of surfactant into a clean diskshaped region, known as holeclosing. We observe that the inward force produces a transient distention, in which the underlying fluid is raised within the closing region. Using a laser line to image the height profile of the fluid surface, we characterize the height and evolution of the fluid distention. We observe that the height of the distension is controlled by a combination of fluid depth, surface tension difference, and chemical composition of both fluid and surfactant. Once formed, the height of the distension decays approximately exponentially, with the timescale primarily set by the particular choice of surfactant and underlying fluid. [Preview Abstract] 

F1.00005: Investigation of thin film coating process for printed electronics with suspension ink by slot die coating SeungHyun Lee, Inyoung Kim Slot die coating process can be easily combined with rolltoroll process and handle various coating liquid with wide range of viscosity and solid content. It is also premetered coating and the thickness of the coated layer can be easily predicted and controlled by a given feed flow rate and coating speed. Therefore, recently, slot die coating process is extending the use of fabrication of thin film printed electronics such as transparent conductive film and thin film solar cell etc. In the present study, we elucidated thin film coating process for printed electronics with suspension ink by slot die coating. Numerical study was investigated the effect of coating die design and rheological characteristics of suspension ink on coating uniformity. Slot die coating experiments was also performed with suspension ink which is composed of Cu(InGa)Se2 nanoparticle and ethanol solvent and compared with numerical simulation. [Preview Abstract] 

F1.00006: Molecular dynamics simulations of the evaporation of particleladen drops Weikang Chen, Joel Koplik, Ilona Kretzschmar We use molecular dynamics simulations to study the evaporation of particleladen droplets on a heated surface. The droplets are composed of a LennardJones fluid containing rigid particles which are spherical sections of an atomic lattice, and heating is controlled through the temperature of an atomistic substrate. We observe that sufficiently large (but still nanosized) particleladen drops exhibit contact line pinning, measure the outward fluid flow field which advects particle to the drop rim, and find that the structure of the resulting aggregate varies with interparticle interactions. In addition, the profile of the evaporative fluid flux is measured with and without particles present, and is also found to be in qualitative agreement with earlier theory. The compatibility of simple nanoscale calculations and micronscale experiments indicates that molecular simulation may be used to predict aggregate structure in vaporative growth processes. [Preview Abstract] 

F1.00007: NonLinear Oscillation in Ionic Current Due to Size Effect in Glass Nanopipette Tomohide Takami, Xiao Long Deng, Jong Wan Son, Eun Ji Kang, Tomoji Kawai, Bae Ho Park We studied the size effect of the ionic current in glass pipette, and found an interesting 2.7 mHz oscillation at 50 nm. In this study, we would like to discuss the mechanism of the nonlinear oscillation. Cationrich layer with its Debye length \textit{$\lambda $} exists in nanopipette, and its conductivity \textit{$\sigma $}$_{d}$ is lower than that in the central bulk layer \textit{$\sigma $}$_{b}$ in this study. The pressure difference \textit{$\Delta $P} = \textit{$\Delta $cRT} where \textit{$\Delta $c} is the difference in concentrations between in and out of the pipette. Then, the ionic current $I$ can be estimated by using HagenPoiseuille equation; \[ I=\frac{\pi }{8\eta }\frac{\Delta cRT}{\ell }\left\{ {\sigma _d r^4+\left( {\sigma _b \sigma _d } \right)\left( {\lambda r} \right)^2\left( {r^2+2r\lambda \lambda ^2} \right)} \right\}. \] ($r$: inner radius, \textit{$\ell $}: pipette length, \textit{$\eta $}: viscosity) The last term indicates the nonlinear oscillation. Moreover, we roughly estimated \textit{$\lambda $} = 2.08$\times $(2$r)^{1/2}$. Then, the bulk layer appears appropriately when 2$r\sim $50 nm, which causes the effective ionic current oscillation. [Preview Abstract] 

F1.00008: Resolving distinct conformations of spectrally similar silverDNA nanoclusters using electrokinetic flows Jackson Del BonisO'Donnell, Deborah Fygenson, Sumita Pennathur SilverDNA nanoclusters (Ag:DNA) are hybrid fluorescent macromolecules in which a silver superatom is stabilized by segments of single stranded DNA in aqueous solution. Recently, electrokinetic separations in microchannels have proven useful for measuring the size and charge of different Ag:DNA emitters stabilized by the same sequence of DNA. Small (50100pL) fluorescent sample plugs are electrokinetically injected down a 30 mm long, 20 $\mu$m deep silica channel in the presence of a buffered backgroundelectrolyte. Fluorophores contained within the injected plug travel at different velocities and thus separate down the length of the channel due to their differences in electrophoretic mobility. Diffusion measurements are also performed in situ by watching the time evolution of a stationary fluorescent sample plug. In the current work, the above techniques are applied to Ag:DNA stabilized by different sequences of DNA designed to adopt similar structures: a 12 cytosine singlestranded loop. Microfluidic separation measurements reveal the presence of multiple, spectrally similar Ag:DNA for different sequences, distinguished by their electrophoretic mobilities. Our results show that both versions of the 12C hairpin motif produce multiple fluorescent species each with different [Preview Abstract] 

F1.00009: Stochastic Analysis of Antibodyantigen Binding in a Microfluidic Device Shauna Adams, Cong Zhang, Harvey Zambrano, A.T. Conlisk Over the last decade, microfluidic ``Labs on a Chip'' (LOC) have evolved from a single microchannel to micrototal analysis systems (TAS) capable of integrating thousands of reaction vessels, conduits and valvesthe contents of an entire chemical laboratoryon a single chip. These systems have several advantages in biomedical applications, including lower equipment and personnel costs, reduced power requirements, faster separations, and smaller sample and reagent volume requirements. Circulating tumor cells (CTC) are cancer cells found in the blood stream indicating the presence of a tumor in the body. We consider the population of magnetically tagged antibodies to be characterized by a collection of stochastic trajectories; the probability of finding an antibody at a given position is assumed to be defined by the FokkerPlanck equation. The first objective is to determine the probability that one or more magnetically labeled antibodies will assume a trajectory that is within the neighborhood of a given cancer cell. Once this occurs the binding process can be described using a deterministic analysis and the modeling of this process is the second objective of the paper. [Preview Abstract] 

F1.00010: Understanding the nonlinearoptical response of a liquidcore photoniccrystal fiber Ilya Fedotov, Vladimir Mitrokhin, Alexander Voronin, Andrey Fedotov, Dmitriy SidorovBiryukov, Aleksey Zheltikov Liquidcore waveguide structures have long been known and intensely used in nonlinear optics. Photoniccrystal fiber (PCF) technologies enhance performance and offer new functionalities of liquid filled waveguides as tools for nonlinear optics. We demonstrate a hollow core PCF that supports singlemode guiding at wavelengths longer than 600 nm in a 4$\mu $mdiameter liquidfilled core, thus offering an attractive platform for nonlinearoptical experiments in the liquid phase. This PCF is employed to demonstrate that liquidphase materials can radically modify the nonlinearoptical response of a waveguide structure relative to a typical nonlinear response of a silica waveguide. We show that the strong inertia of optical nonlinearity, characteristic of highly nonlinear liquidphase materials, gives rise to a pulsewidth dependent spectral red shift of the spectrally broadened fiber output. This wavelength shift remains strong even for pulse widths as large as several hundreds of femtoseconds. [Preview Abstract] 

F1.00011: Onchip Micro and Nanofluidic Electrokinetic Injection and Separation for PEGylation Analysis Elijah Shelton, Mary Baum, Dan Morse, Sumita Pennathur We present an experimental study of micro and nanofluidic electrokinetic injection and separation in borosilcate channels as a method for characterizing size and zeta potential of biomoleculesspecifically polyethlylene glycol (PEG), keyhole limpet hemocyanine (KLH), and pegylated KLH. While pegylation (the conjugation of proteins with PEG) is an established technique for enhancing a protein's therapeutic properties, reliable characterization of these conjugations by traditional analysis techniques (i.e. gelelectrophoresis, zetasizer) remains a challenge. Using a threestep electrokinetic sequence (load, gate, and inject), FITC labeled species and a fluorescein tracer dye are injected into a channel where they separate according to differences in electrophoretic mobility. We find the average absolute mobility of pegylated subunit KLH in 1 micron channels to be 56\% that of unpegylated subunit KLH. In a 250 nm channel, we measure a 33\% shift in the average absolute mobility of PEG dendrimers as compared to measurements in a 1 micron channel. These results begin to demonstrate how a micro and nanofluidicbased approach might address the demand for effective and accessible nanoparticle characterization platforms. [Preview Abstract] 

F1.00012: The Clogging Behavior of Tapered Microchannels Sorell Massenburg, Kaare Jensen, David Weitz Nearly every application involving fluid relies upon filtration, yet filter design is not well understood. Design features, such as shape and pore size distribution, can be modeled in two dimensions using soft lithographic techniques to fabricate microscale pores in polydimethylsiloxane. We are then able to characterize the efficacy of variations in pore design by clogging these pores with polystyrene microparticles stabilized by carboxyl surface groups. Previous studies show that a probabilistic model based upon the Poiseuille Law well describes straight microfluidic channels clogged via hard spheres that are smaller than the channel. This model predicts that clogging behavior determined by the smallest dimension of the pore (the constriction). We show that tapered microfluidic channels modeled after pores in filter membranes do not follow this model and investigated the differences. Contrasting our results to the aforementioned probabilistic model helps elucidate the function of certain filter design features. [Preview Abstract] 

F1.00013: Fluid Surface Deformation by Objects in the Cheerios Effect Khoi Nguyen, Michael Miller, Shreyas Mandre Small objects floating on a fluid/air interface deform of the surface depending on material surface properties, density, and geometry. These objects attract each other through capillary interactions, a phenomenon dubbed the ``cheerios effect.'' The attractive force and torque exerted on these objects by the interface can be estimated if the meniscus deformation is known. In addition, the floating objects can also rotate due to such an interaction. We present a series of experiments focused on visualizing the the motions of the floating objects and the deformation of the interface. The experiments involve thin lasercut acrylic pieces attracting each other on water in a large glass petri dish and a camera setup to capture the process. Furthermore, optical distortion of a grid pattern is used to visualize the water surface deformation near the edge of the objects. This study of the deformation of the water surface around a floating object, of the attractive/repulsive forces, and of postcontact rotational dynamics are potentially instrumental in the study of colloidal selfassembly. [Preview Abstract] 

F1.00014: Shape Control of Doctor blade coated Polymer Electrodes via Microflow Control in a Drying Droplet Yunseok Jang, Jeongdai Jo, SeungHyun Lee We demonstrated a simple patterning method for polymer electrodes such as poly(3,4ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) by using the doctor blade coater. We controlled the surface tension for controlling the polymer electrodes shape. We made use of the difference in wettability between hydrophobic surfaces and hydrophilic surfaces to make the polymer electrodes patterns. However, the polymer electrodes patterns made with our patterning method created undesirable ringlike stains, which were caused by the outward flow of the solute within the PEDOT/PSS solution drop. To achieve homogenous device performance, we proposed a simple process for removing this ringlike stain by making the surface tension gradient in the PEDOT/PSS solution drop. Because this surface tension gradient causes the inward flow of the solute within the PEDOT/PSS solution drop, the ringlike stain is removed. Finally, we confirmed the potential of our patterning method for polymer electrodes such as the PEDOT/PSS by fabricating pentacene thinfilm transistors (TFTs) and measuring the electrical properties of the pentacene TFTs. [Preview Abstract] 

F1.00015: Electrical Power Generation by Mechanically Modulating Electrical Double Layers Dongyun Lee, Jong Kyun Moon, Jaeki Jeong, Hyuk Kyu Pak Many objects in contact with a liquid acquire some electronic charges on their surfaces. These charges on the surface attract counter ions from the liquid phase. This complex system is called electrical double layer (EDL). Since its geometry and structure is similar to an electric capacitor, it is also called an electrical double layer capacitor (EDLC). In this work we studied two EDLCs formed in a liquid droplet bridge between two parallel solid conducting plates. We found that when the bridge height was mechanically modulated, each EDLC was continuously charged and discharged generating an AC electric current across the plates. The results of this experiment can be useful for constructing a microfluidic power generation. [Preview Abstract] 

F1.00016: Direct numerical simulation of currentinduced convection near an ionselective surface Clara Druzgalski, Mathias B. Andersen, Ali Mani Understanding fundamentals of electrokinetic transport and fluid flow phenomena near ionselective surfaces provides insight to improve systems such as electrodialysis for water deionization. The work of Rubinstein and Zaltzman [e.g. Phys Rev E 62, 2238 (2000)] have clarified qualitative aspects of how development of currentinduced spacecharge layers near ionselective surfaces can lead to the onset of electroosmotic instabilities. We expand on this work through multidimensional numerical simulation of the full nonlinear PoissonNernstPlanck and NavierStokes equations with ideally selective membrane boundary conditions. Our numerical scheme is optimized by exploiting the periodicity in the system parallel to the ionselective surface, using a spectral method in these coordinates. In the wall normal direction a finite difference approach accurately captures the strongly nonlinear nested boundary layer structure. Our numerical scheme fully resolves the concentration profiles throughout the system including the numerically stiff electric double layer and extended space charge layer. Our simulations enable prediction of the full continuous current versus voltage curves showing overlimiting current without resorting to any adjustable parameter. [Preview Abstract] 

F1.00017: Soretdriven convection in colloidal suspensions Mahmoud DarAssi, Layachi Hadji Convection in colloidal suspensions of solid particles is characterized by the interplay between thermophoresis, sedimentation and Brownian diffusion. Their coupled effects is represented by a dimensionless parameter $\beta$ and experiments by Chang {\it et al.} (2008) have shown that for a given set of experimental parameters, $\beta$ is a function of the particle radius $r_p$ with the function $\beta(r_p)$ having the shape of an inverted parabola with two roots in the range $ 5$ nm $\le r_p \le 125$ nm. We investigate both the linear and nonlinear convection in a suspension of solid particles using a particulate medium in a RayleighB\'{e}nard geometry setup. The analysis focuses on the particle dominated convection regime for which the onset is steady and to disturbances having infinitely long wavelength. For $0 < \beta \ll 1$, which corresponds to particle size near the two roots of $\beta(r)$, we retrieve the instability threshold conditions for the binary mixture model. For $\beta = O\bigl(1\bigr)$, we show that, unlike the binary mixture model, the conditions for instability onset can be mapped to corresponding experimental parameters. A nonlinear evolution equation is derived and its predictions compared to those of a similar equation for the binary mixture case. [Preview Abstract] 

F1.00018: Super free fall in a semiinfinite cone filled with a low viscosity liquid Ayax Torres, Guadalupe Gutierrez, Abel LopezVilla, Abraham Medina The super free fall of a lowviscosity liquid column, filling partially a section of a vertical conical tube of nonfinite length, it is analyzed. Through the use of an inviscid and onedimensional model for the flow we describe the complex simultaneous motion of the two liquid interfaces. [Preview Abstract] 

F1.00019: The thinning of viscous liquid threads. J. Rafael CastrejonPita, Alfonso A. CastrejonPita, Ian M. Hutchings The thinning neck of dripping droplets is studied experimentally for viscous Newtonian fluids. High speed imaging is used to measure the minimum neck diameter in terms of the time $\tau$ to breakup. Mixtures of water and glycerol with viscosities ranging from 20 to 363 mPa s are used to model the Newtonian behavior. The results show the transition from potential to inertialviscous regimes occurs at the predicted values of $\sim$Oh$^2$. Before this transition the neck contraction rate follows the inviscid scaling law $\sim \tau^{2/3}$. After the transition, the neck thinning tends towards the linear viscous scaling law $\sim \tau$. [Preview Abstract] 

F1.00020: Spreading and Fragmenting Characteristics of Impacting Droplet on Micro/ Nanostructured WaterRepellent Surfaces Hyungmo Kim, Chan Lee, Moo Hwan Kim, Joonwon Kim After impact on a solid surface a droplet spreads, but in different ways such as deposition, rebound, and fragmentation. Because fragmentation occurs when the kinetic energy beat the surface energy during impact, Weber number is the most important dimensionless number in the rebound/fragmentation criteria. This also can be dramatically changed by the micro/nanoscale surface structures. Different micro/nanostructured surfaces were fabricated using silicon wet etching, black silicon formation, or the combination of these methods. Then, spreading and fragmenting events were analyzed with supporting experimental results. On the surfaces, the microstructures form obstacles to drop spreading and retracting, the nanostructures give extreme waterrepellency, and the hybrid micro/nanostructures facilitate droplet fragmentation. Especially, the CassieBaxter's fraction factor of the microstructures can change rebound/fragmentation criteria. From this work, we finally investigate how the micro/nanostructures can change spreading and fragmenting dynamics during droplet impact. [Preview Abstract] 

F1.00021: Enhanced two photon fluorescence microfluidic sensor based on dual cladding photoniccrystal fiber Lyubov Amitonova, Ilya Fedotov, Andrey Fedotov, Aleksei Zheltikov The architecture of photoniccrystal fibers (PCFs) suggests a variety of strategies for optical sensing. A combination of TPA approaches with capabilities of fiberoptic probes offers numerous advantages, suggesting a convenient format for beam delivery, facilitating manipulation of excitation radiation, and allowing this excitation to be applied locally and selectively. In this work, we show that a PCF with a special design can realize different protocols of optical sensing, simultaneously serving, whenever necessary, for the collection and online monitoring of liquidphase samples. Specially designed PCF is shown to substantially increase the guidedwave luminescent response from molecules excited through twophoton absorption (TPA) by femtosecond nearinfrared laser pulses. Biophotonic implications of this waveguide TPLresponse enhancement include fiberformat solutions for online monitoring of drug delivery and drug activation, interrogation of neural activity, biosensing, endoscopy, and locally controlled singlet oxygen generation in photodynamic therapy. [Preview Abstract] 

F1.00022: Speed of a Taylor Swimmer in Newtonian and Viscoelastic Fluids Moumita Dasgupta, Bin Liu, Henry Fu, Michael Berhanu, Kenneth Breuer, Thomas Powers, Arshad Kudrolli We demonstrate that the speed of an idealized Taylor swimmer with a prescribed waveform in a viscoelastic fluid can be greater or lesser than in a Newtonian fluid depending on their rheological properties. The measurements are performed using a cylindrical sheet immersed in a fluid inside a cylindrical tank under torque free conditions with traveling waves imposed in the azimuthal direction. Swimming speeds in the Newtonian case are found to be consistent with calculations using the Stokes equation. A faster swimming speed is found in a viscoelastic fluid which has a constant viscosity with shear rate. By contrast, a slower swimming speed is found with more complex shear thinning viscoelastic fluids which have multiple relaxation time scales. These results are compared with calculations with OlroydB fluids which find a decreasing swimming speed with Deborah Number given by the product of fluid elastic relaxation time scale and the driving frequency. [Preview Abstract] 

F1.00023: Interaction between shape and lipid flow in bilayer membranes Padmini Rangamani, Ashutosh Agrawal, Kranthi Mandadapu, George Oster, David Steigmann Biological membranes have unique mechanical properties: they are fluid inplane but elastic in bending. The most popular continuum mechanics model of the lipid bilayer is the Helfrich model. This model has provided insight into many membrane phenomena. However, it is an equilibrium model for an elastic membrane and does not capture any dynamic effects. The theory of intrasurface viscous flow on lipid bilayers is developed by combining the equations for flow on a curved surface with those that describe the elastic resistance of bilayers to flexure. The model is derived directly from balance laws and thus augments alternative formulations based on variational principles. Conditions holding along an edge of the membrane are emphasized and the coupling between flow and membrane shape is simulated numerically. Simulations of the model show that membrane shape changes involve the interaction between flow and surface deformation that are intrinsically nonlinear effects. In response to an applied lateral pressure normal to the membrane, the shape of the membrane changes. Simultaneously, the surface flow field evolves over time to accommodate the deformation. Using this model, we can study the formation of membrane tubes and many biological phenomena. [Preview Abstract] 

F1.00024: Oscillationinduced drop transport using lowfrequency ac electrowetting Jiwoo Hong, Seung Jun Lee, Kwan Hyoung Kang When a small drop starts to move contact angle hysteresis (CAH) manifests as a pinning force and hinders the drop transport on a solid surface. For such a reason, many researchers have been studying how to reduce CAH. On the contrary, we demonstrate that small drops on an inclined plane can be mobilized by utilizing CAH and drop oscillations driven by ac electrowetting rather than reducing CAH. By using the peculiar dependence of sliding velocity on the size of a drop and the applied ac frequency, we can selectively slide drops of a specific size or merge two volumetrically different drops along an inclined plane. In addition, the direction of drop motion is determined by the initial asymmetry of contact angles on both edges of a drop. Accordingly, small drops can climb up an inclined plane using lowfrequency ac electrowetting when the initial asymmetry of contact angles is reversed. We also obtain the threshold voltage for a climbing drop and the empirical relationship between the applied voltage and the climbing velocity. [Preview Abstract] 

F1.00025: A pipette dispenses a charged droplet Dongwhi Choi, Horim Lee, Do Jin Im, In Seok Kang, Kwan Hyoung Kang Micropipettes are widely used in many scientific and engineering fields. However, it is hardly known that a droplet dispensed from a plastic pipette tip has a considerable amount of charges (order of 1010 C). Here we report that the charged droplet is dispensed from a commercial and disposable plastic pipette tip and this charge is originated from the natural electrification between a solution and the inner surface of the pipette tip. The charge amount is dependent on not only the physicochemical properties of a solution (e.g., pH and a concentration) but also dispensing environments (e.g., atmospheric humidity and type of commercial pipette tip). To investigate the effects of the charge on the droplet dispensing, we calculate the electrical force between the droplet and the pipette tip though numerical simulation. The micropipette users especially, who are dealing with discrete droplets in their experiments, should consider this charge effect in their dispensing of a droplet. [Preview Abstract] 

F1.00026: An Experimental Study of the Effect of Viscosity on Bouncing Soap Droplets onto a Horizontal Soap Film AmyLee Gunter, Hoi Dick Ng This experimental study aims to investigate the phenomenon of a bouncing soap droplet on a horizontal soap film, and how this behavior is affected by variations in the glycerol content of the solution for both the droplet and film. Direct visualization of the bouncing dynamics using highspeed photography allows determination of droplet size and rebound height as the viscosity is varied. In addition, the upper and lower limits of the mixture composition at which the viscosity of the fluid prevents the droplet from bouncing are determined. A thorough examination of this fluid trampoline was recently conducted by Gilet and Bush, the focus of which was to compare the effect of vibration in the soap film [T. Gilet and J.W.M. Bush, J. Fluid Mech. 625: 167203, 2009]. A small amount of attention was given to the effect of viscosity changes in the droplet and film, and this work aims to expand on those findings. [Preview Abstract] 

F1.00027: Nonlinear dynamics in a microfluidic loop device: Chaos and Fractals Jeevan Maddala, Raghunathan Rengaswamy Discrete decision making and resistive interactions between droplets in a microfluidic loop device induces fascinating nonlinear dynamics such as multistability and period doubling. Droplets entering the device at fixed time intervals can exit at different periods or chaotically. One of the periodic behaviors that is observed in a loop is the threeperiod behavior; this is consistent with the notion that three period behavior implies chaos. Switching between these different dynamical regimes is achieved by changing the inlet droplet feeding frequency. Chaotic behavior is observed between islands of periodic behavior. We show through simulations and experimental observations that the transitions between periods are indeed chaotic. Network model is used to study the dynamic behavior for different inlet feeding frequencies resulting in the development of a bifurcation map. The bifurcation map shows that the three period dynamics is preceded by chaos. A Lyapunov exponent is used to further validate these results. The exit droplet spacing shows several fascinating patterns when the model is simulated for a large number of droplets in the chaotic regime. One such chaotic regime produces a fractal that has a boundary of cardioid. The correlation dimension for a fractal pattern produced by this particular loop system is calculated to be 0.7. [Preview Abstract] 

F1.00028: Accumulation of BSA in Packedbed Microfluidics Samantha Summers, Chuntian Hu, Ryan Hartman Alzheimers and Parkinsons are two diseases that are associated with protein deposition in the brain, causing loss of either cognitive or muscle functioning. Protein deposition diseases are considered progressive diseases since the continual aggregation of protein causes the patient's symptoms to slowly worsen over time. There are currently no known means of treatment for protein deposition diseases. Our goal is to understand the potential for packedbed microfluidics to study protein accumulation. Measurement of the resistance to flow through microscale packedbeds is critical to understanding the process of protein accumulation. Aggregation in bulk is fundamentally different from accumulation on surfaces. Our study attempts to distinguish between either mechanism. The results from our experiments involving protein injection through a microfluidic system will be presented and discussed. [Preview Abstract] 

F1.00029: Measurement of the extensional viscosity for Newtonian and and viscoelastic liquids using the selective withdrawal technique E. TrejoPeimbert, R. Zenit, J.J. Feng Extensional viscosity is hard to measure. None of the existing devices offers a definite solution to determine this property for both viscous and viscoelastic liquids. This is the main motivation of this investigation: to find an alternative and reliable method to measure this property. We propose the use of a device inspired in the wellknown selective withdrawal system. A viscous fluid is withdrawn near the interface from below with a tube. The suction generates the deformation of the free surface and the flow beneath is largely extensional. We conducted measurements of the extension rate using PIV and measured the surface deformation to infer the extensional stress. By knowing these two quantities the value of the extensional viscosity is calculated. We present the measurements obtained for both viscous Newtonian and several non Newtonian fluids. For Newtonian fluids, we do obtain measurements of the Trouton ratio close to 3. We observe a variety of interesting behaviors for non Newtonian liquids, which will be presented and discussed. [Preview Abstract] 

F1.00030: Optoelectrokinetic trapping of Gold Nanoparticles for SERS Applications Avanish Mishra, Raviraj Thakur, Stuart Williams, Aloke Kumar, Steve Wereley Gold or Silver nanoparticle based Microfluidic Surface Enhanced Raman Spectroscopy (SERS) provides an excellent platform for sensitive chemical and biomolecular detection. Microfluidic SERS requires metal nanoparticles to be accumulated in a controlled manner. In this work, we present an active optoelectrokinetic method for patterning gold nanoparticles on a planar electrode surface. This technique consists of two indium tin oxide (ITO) electrodes across which an AC electric field is applied. Gold nanocolloidal solution is filled between the electrodes. Projection of an infrared (1064 nm) laser beam on one of the electrode surfaces causes a perturbation in electrical conductivity and permittivity of the fluid which in turn creates microscopic flow instability and an electrothermal vortex is generated. The electrothermal vortex traps gold nanoparticles and brings them closer to the electrode surface by hydrodynamic drag force where nanoparticles are trapped by particleelectrode interactions. This leads to an accumulation of gold nanoparticles at the site of illumination which can be used as a SERS hot spot. [Preview Abstract] 

F1.00031: Experimental Results of Electrothermal Vortex in Parallel ITOglass With High Conductivity Medium and AC electric field and Laser Jupyoung Kim, Jaesung Kwon, Steve Wereley In many previous works, diverse experiments about Electrothermal Vortex were done because ac dc electrokinetic manipulation of particles became an important research area and Electrothermal Vortex is a major part of the electrokinetics. Especially in this work, however, Electrothermal Vortex was observed in parallel two ITOglass with high conductivity medium (the medium was potassium chloride~(KCl)). Because of high conductivity of potassium chloride and micro characteristic length scale of ITOglass, effect of joule heating is significant. Then, this influences on Electrothermal Vortex. In addition, the previous works were done by complicated form of electrodes in order to make nonuniform electric fields. Making theses electrode shape is too fastidious to do readily, while our work is very simple so that it is proper to any type of applications. According to PeaktoPeak voltage, Frequency, and Laser power, we measured shape and velocity of Electrothermal Vortex, Basically, Electrothermal Vortex was not related with AC frequency, but was proportional to PeaktoPeak voltage and Laser power. [Preview Abstract] 

F1.00032: BIOFLUIDS 

F1.00033: Simultaneous analysis of wake structure and force measurements of unsteady hydrofoils Timothy Jeter, Jr., Melissa Green In the field of bioinspired hydrodynamics, comparison of simultaneous wake structure analysis and force measurement on the body itself are relatively unexplored. Hydrofoil technology in an experimental setup seeks to bridge this gap, with water tunnel experiments that utilize a pitching and heaving lowaspectratio airfoil mounted vertically. The actuation is accomplished by employing a twoaxis motion controller. Vortical wake structure will be analyzed using particle image velocimetry (PIV), and hydrodynamic forces will be measured using a sixcomponent force balance installed within the actuation system. The simultaneous measurements will allow for correlation of wake structure to propulsive power and efficiency and evaluate their relationship with variations in Strouhal number and Reynolds number. [Preview Abstract] 

F1.00034: Characterization of Surface Acoustic Wave Nebulization: Atomization dynamics and resulting droplet size distribution Alicia Clark, Alberto Aliseda, Scott Heron, Yue Huang, David Goodlett Highspeed imaging and Phase Doppler Particle Analyzer (PDPA) measurements are used to characterize the size and velocity distributions of micronsized droplets produced by a surface acoustic wave (SAW) microelectronic nebulizer. The effects of drop composition, electric field amplitude and pulsation frequency, and initial drop volume have been experimentally studied. We observe that the droplets created in pure water are smaller, $\sim $2 $\mu $m, and the plume more concentrated near the nebulizer, with small second probability peak for large diameters, $\sim $100 $\mu $m. Pure methanol droplets have larger diameters, $\sim $ 5 $\mu $m, and lower volume concentration in the nebulizer plume, as corresponds to less efficient atomization process. The influence of fluid viscosity and surface tension will be discussed. Measurements of the velocity distribution show a strong dependency with excitation amplitude and duty factor. [Preview Abstract] 

F1.00035: Thermodynamic of cellulose solvation in novel solvent mixtures Ritankar Das Biomass contains abundant amounts of cellulose as crystalline microfibrils. A limiting step to using cellulose as an alternative energy source, however, is the hydrolysis of the biomass and subsequent transformation into fuels. Cellulose is insoluble in most solvents including organic solvents and water, but it is soluble in some ionic liquids like BMIMCl. This project aims to find alternative solvents that are less expensive and are more environmentally benign than the ionic liquids. Allatom molecular dynamics simulations were performed on dissociated glucan chains separated by multiple (45) solvation shells, in the presence of several novel solvents and solvent mixtures. The solubility of the chains in each solvent was indicated by contacts calculations after the equilibration of the molecular dynamics. It was discovered that pyridine and imidazole acted as the best solvents because their aromatic electronic structure was able to effectively disrupt the intersheet interactions among the glucan chains in the axial direction, and because perturbation of the solvent interactions in the presence of glucan chains was minimal. [Preview Abstract] 

F1.00036: A Computational Model of Optimal Vein Graft Adaptation in an Arterial Environment Abhay B. Ramachandra, Sethuraman Sankaran, Jay Humphrey, Alison Marsden In coronary artery disease, surgical revascularization using venous bypass grafts is performed to relieve symptoms and prolong life. Coronary bypass graft surgery is performed on approximately 500,000 people every year in the United States, with graft failure rates as high as 50{\%} within 5 years. When a vein graft is implanted in the arterial system it adapts to the high flow rate and high pressure of the arterial environment by changing composition and geometry, and thus stiffness. Hemodynamic loads, resulting in altered wall shear and intramural stresses, are major factors impacting vein graft remodeling. Here, a constrained mixture theory of growth and remodeling for arteries is extended to model the evolution of a vein graft subjected to arterial flow and pressure conditions. A derivativefree optimization method is used to estimate the optimal set of constitutive parameters that best match passive biaxial mouse inferior vena cava data from experiments. Optimization is performed using surrogate management framework, a pattern search method with established convergence theory. The resulting parameter set is used to predict optimal vein adaptation in an arterial environment for two illustrative cases: a) Step change b) Gradual change in loading. Results are compared against vein graft data from the literature and a possible set of mechanisms for suboptimal vein graft remodeling is suggested. [Preview Abstract] 

F1.00037: Deformation of Congenital Bicuspid Aortic Valves in Systole Kai Szeto, Peter Pastuszko, Vishal Nigam, Juan Lasheras Clinical studies have shown that patients with congenital bicuspid aortic valves (CBAVs) develop degenerative calcification of the leaflets at young ages compared to normal tricuspid aortic valves (TAVs). It has been hypothesized that the asymmetrical geometry of the leaflets in CBAVs and the associate changes in flow shear stresses and excessive strain rate levels are possible causes for the early calcification. Central to the validation of this hypothesis is the need to quantify the differences in strain rate levels between the BAVs and TAVs. We simulate the CBAVs by surgically stitching two of the leaflets of a porcine aortic valve together. To quantify strain differences, we performed invitro experiments in both BAVs and TAVs by tracking the 3D motion of small dots marked on each leaflet surface. We then used phaselocked stereo photogrammetry to measure the strain rates in both radial and circumferential directions during the whole cardiac cycle. In the BAVs' case, the fused leaflet experiences an almost 30{\%} increase in the radial stretching when fully open. RNA profiling of human aortic valve interstitial cells exposed to cyclic stretch shows that the increased stretch experienced by the BAVs results in increased levels of INTERLEUKINS (ILs) and other known inflammatory markers associated with aortic valve calcification. Together, these observations suggest that the abnormal stretch experienced by BAVs activates inflammation gene expression. [Preview Abstract] 

F1.00038: ABSTRACT WITHDRAWN 

F1.00039: Characterization of intraventricular flow patterns in healthy neonates from conventional colorDoppler ultrasound Shai TejmanYarden, Callie Rzasa, Yolanda Benito, Marta Alhama, Tina Leone, Raquel Yotti, Javier Bermejo, Beth Printz, Juan C. del Alamo Left ventricular vortices have been difficult to visualize in the clinical setting due to the lack of quantitative noninvasive modalities, and this limitation is especially important in pediatrics. We have developed and validated a new technique to reconstruct twodimensional timeresolved velocity fields in the LV from conventional transthoracic colorDoppler images. This noninvasive modality was used to image LV flow in 10 healthy fullterm neonates, ages 2448 hours. Our results show that, in neonates, a diastolic vortex developed during LV filling, was maintained during isovolumic contraction, and decayed during the ejection period. The vortex was created near the base of the ventricle, moved toward the apex, and then back toward the base and LVOT during ejection. In conclusion, we have characterized for the first time the properties of the LV filling vortex in normal neonates, demonstrating that this vortex channels blood from the inflow to the outflow tract of the LV. Together with existing data from adults, our results confirm that the LV vortex is conserved through adulthood. [Preview Abstract] 

F1.00040: Forewinghindwing phaselag effect in the propulsive performance of a fourwinged flapping flyer Mariana Centeno, Daniel Pradal, Benjamin Thiria, Ramiro GodoyDiana We study experimentally a fourwinged flapping flyer with chordwise flexible wings in a selfpropelled configuration. For a given physical configuration of the flyer (i.e. fixed distance between the forewing and hindwing pairs and fixed wing flexibility), we explore the kinematic parameter space constituted by the flapping frequency and the forewinghindwing phase lag. Net thrust force, cruising speed and consumed electric power measurements were performed for each point in the $(f,\varphi)$ parameter space. These results are analyzed in parallel with twodimensional velocity field measurements obtained by timeresolved particle image velocimetry around a forewinghindwing pair. [Preview Abstract] 

F1.00041: Threedimensional flow around a hovering hummingbird Jialei Song, Haoxiang Luo, Tyson Hedrick We use an immersedboundary method to simulate the complex threedimensional flow around a hovering hummingbird and study the unsteady vortical structures in the flow. In the simulation, the realistic wing kinematics is reconstructed from highspeed imaging data of a Rufous hummingbird, and thus the wing surface does not assume a twodimensional plane. The Reynolds number is approximately 3000 based on the average wingtip velocity and the mean cord length. More than 16 million Cartesian mesh points are used in the simulation, which allows us to capture both near and farfield vortices. We will show the detailed flow structures in the presentation and will compare the numerical result with previous experimental measurement. In addition, we will discuss the force characteristics and the aerodynamic power of the bird. [Preview Abstract] 

F1.00042: Understanding cell passage through constricted microfluidic channels Marco A. CartasAyala, Rohit Karnik Recently, several microfluidic platforms have been proposed to characterize cells based on their behaviour during cell passage through constricted channels. Variables like transit time have been analyzed in disease states like sickle cell anemia, malaria and sepsis. Nevertheless, it is hard to make direct comparisons between different platforms and cell types. We present experimental results of the relationship between solid deformable particle properties, i.e. stiffness and relative particle size, and flow properties, i.e. particle's velocity. We measured the hydrodynamic variables during the flow of HL60 cells, a white myeloid cell type, in narrow microfluidic square channels using a microfluidic differential manometer. We measured the flow force required to move cells of different sizes through microchannels and quantified friction forces opposing cell passage. We determined the nondimensional parameters that influence the flow of cells and we used them to obtain a non dimensional expression that can be used to predict the forces needed to drive cells through microchannels. We found that the friction force needed to flow HL60 through a microfluidic channel is the sum of two parts. The first part is a static friction force that is proportional to the force needed to keep the force compressed. The second part is a factor that is proportional to the cell velocity, hence a dynamic term, and slightly sensitive to the compressive force. [Preview Abstract] 

F1.00043: Continuousflow separation of live and dead yeasts using reservoirbased dielectrophoresis (rDEP) Saurin Patel, Daniel Showers, Pallavi Vedantam, TzuenRong Tzeng, Shizhi Qian, Xiangchun Xuan Separating live and dead cells is critical to the diagnosis of early stage diseases and to the efficacy test of drug screening etc. We develop a novel microfluidic approach to continuous separation of yeast cells by viability inside a reservoir. It exploits the cell dielectrophoresis that is induced by the inherent electric field gradient at the reservoirmicrochannel junction to selectively trap dead yeasts and continuously sort them from live ones. We term this approach reservoirbased dielectrophoresis (rDEP). The transporting, focusing, and trapping of live and dead yeast cells at the reservoirmicrochannel junction are studied separately by varying the DCbiased AC electric fields. These phenomena can all be reasonably predicted by a 2D numerical model. We find that the AC to DC field ratio for live yeast trapping is higher than that for dead cells because the former experiences a weaker rDEP while having a larger electrokinetic mobility. It is this difference in the AC to DC field ratio that enables the viabilitybased yeast cell separation. The rDEP approach has unique advantages over existing DEPbased techniques such as the occupation of zero channel space and the elimination of inchannel mechanical or electrical parts. [Preview Abstract] 

F1.00044: ABSTRACT WITHDRAWN 

F1.00045: Establishing live cell directional 2point particle tracking microrheology Ricardo Serrano, Manuel GomezGonzalez, Juan C. del Alamo Directionality is essential for cell function and relation with its environment: an isotropic cell would not be able to move, mechanotransduct or perform any action other than isotropic compression and expansion. Cell directionality is achieved through chemical gradients and mechanical orientation of the cytoskeleton. The directional mechanics of the cell cytoplasm is described by the LeslieEricksen equations, dependent on the 3 Miesowicz viscoelasticity coefficients. They can be measured by using Directional Particle Tracking Microrheology. However, the 3D motion of a particle in a nematic environment provides only 2 independent equations, and only 2 viscoelasticity coefficients could previously be calculated, i.e. by tracking a single particle, we could only fully describe a pseudoisotropic fluid. In this study, we analyze the motion of two microspheres in a directional nematic fluid. The medium is composed of an elastic directional network viscously coupled to a viscous isotropic liquid. The correlated motion of the two microspheres provide 3 independent equations. These equations can be used to measure the 3 directional viscosity coefficients. We show that, by using Directional 2Point PTM, we can determine the complete microrheology of a nematic material. [Preview Abstract] 

F1.00046: Comprehensive Spatial Display of the Microcirculation in a Capillary Bundle from Rat Spinotrapezius Muscle Fascia Tissue Niki Yamamura, Frank Jacobitz, Geert SchmidSch\"onbein Previous investigations of the microcirculation in skeletal muscle have utilized a statistical display of fundamental hemodynamic variables without regard of actual microvascular details. The focus of this project is the development of a software tool to perform a spatial analysis of hemodynamic results. The vessel network considered in this study is a capillary bundle in rat spinotrapezius muscle fascia with transverse arterioles supplying blood, capillary vessels, and collecting venules removing blood. The software tool represents information about blood vessel location and connectivity in two matrices. The first matrix holds spatial locations of vessel intersections or nodes. This matrix is used to create a second matrix containing the locations of all microvessels. The second matrix is then used to produce result matrices holding the values of flow properties at the locations at which they are observed in the vessel network. The resulting images provide a full display, for example, of the pressure drop in the network. The highest velocities are obtained in the transverse arterioles and adjacent capillaries, while other vessels in the network show lower velocities. An area of elevated hematocrit is observed in the periphery of the network. [Preview Abstract] 

F1.00047: Simulations of the Microcirculation in the Human Conjunctiva William Dow, Frank Jacobitz, Peter Chen The microcirculation in the conjunctiva of a healthy human subject is analyzed using a simulation approach. A comparison between healthy and diseased states may lead to early diagnosis for a variety of vascular related disorders. Previous work suggests that hypertension, arteriosclerosis, and diabetes mellitus have noticeable very early changes in the microvasculature (Davis and Landau, 1957; Ditzel, 1968; Kunitomo, 1974) and the vessels of the conjunctiva are specifically useful for this research because they can be studied noninvasively. The microcirculation in the conjunctiva has been documented over the course of disease treatments, providing both still images and video footage for information on vessel length, diameter, and connectivity as well as the direction of blood flow. The numerical method is based on a HagenPoiseuille balance in the microvessels and a sparse matrix solver is used to obtain the solution. The simulations use realistic vessel topology for the microvasculature, reconstructed from microscope images of tissue samples, and consider blood rheology as well as passive and active vessel properties. [Preview Abstract] 

F1.00048: Proteins at flowing interfaces: From understanding structure to treating disease David Posada, James Young, Amir Hirsa The field of soft matter offers vast opportunities for scientific and technological developments, with many challenges that need to be addressed by various disciplines. Fluid dynamics has a tremendous potential for greater impact, from broadening fundamental understanding to treating disease. Here we demonstrate the use of fluid dynamics in two biotechnology problems involving proteins at the air/water interface: a) 2Dimensional protein crystallization and b) amyloid fibril formation. Protein crystallization is usually the most challenging step in Xray diffraction analysis of protein structure. Recently it was demonstrated that flow can induce 2D protein crystallization at conditions under which quiescent systems do not form crystals. A different form of protein structuring, namely amyloid fibrillization, is also of interest due to its association with several neurodegenerative diseases such as Alzheimer's and Parkinson's disease. Protein denaturation, which is the root of the fibrillization process, is also a significant concern in biotherapeutics production. Both problems are studied by using shearing freesurface flows in simple geometries. The common finding is that flow can significantly enhance the growth of protein structures. [Preview Abstract] 

F1.00049: Separation control effects of mako shark skin applied to NACA 4412 hydrofoil and a cylinder Michael Bradshaw, Amy Lang, Philip Motta, Maria Habegger, Robert Hueter Shark skin is investigated as a means of passive flow separation control due to its preferential flow direction and the potential for its scales to obstruct lowmomentum backflow resulting from an adverse pressure gradient. In this study, the effect of the scales on flow reversal is primarily observed in a tripped turbulent boundary layer by comparing the flow over a NACA 4412 hydrofoil with a smooth, painted surface to that over the same hydrofoil with samples of mako shark skin affixed to its upper surface. Also, the effect of the scales on unsteady flow reversal is observed in laminar flow conditions for flow over a cylinder covered with mako shark skin. These samples were taken from the shark's flank region because the scales at that location have been shown to have the greatest angle of bristling, and thus the best potential for separation control. All sets of flow data in this study were obtained using TimeResolved Digital Particle Image Velocimetry. The flow was primarily analyzed by means of the backflow coefficient (a value based on the percentage of time that flow in a region over the hydrofoil is reversed), average backflow magnitude, and the time history of instantaneous flow velocity values at specific points in the boundary layer over the hydrofoil models. [Preview Abstract] 

F1.00050: DPPC: Is it ever Newtonian? Amir Sadoughi, Amir Hirsa, Juan Lopez Understanding the intrinsic properties of lung surfactant constituent components is important for a scientific foundation and predictive models. The three major interfacial properties affecting the hydrodynamics are surface tension, surface shear viscosity $\mu^s$, and surface dilatational viscosity $\kappa^s$. At small scales such as in the alveoli, the effects of the interfacial viscosities are comparable to those of surface tension gradients. The surface tension can be determined reliably using a variety of methods. There are also several techniques that lead to consistent measurements of surface shear viscosity. Recently, for DPPC (the most prevalent constituent of lung surfactant), Newtonian behavior was demonstrated for several monolayer phases, and nonNewtonian flow documented for other phases. On the other hand, the surface dilatational viscosity is difficult to quantify, and no systematic measurements have been reported. We utilize a freesurface cavity with fixed sidewalls and oscillatory driven floor to measure the response of the monolayer. The sum $\mu^s+\kappa^s$ is deduced from comparisons between the experiments and NavierStokes computations with BoussinesqScriven surface model. Subsequently, the independent measurements of $\mu^s$ are used to isolate $\kappa^s$. [Preview Abstract] 

F1.00051: NonDimensional Formulation of Ventricular WorkLoad Severity Under Concomitant Heart Valve Disease Melody Dong, Rachael SimonWalker, Lakshmi Dasi Current guidelines on assessing the severity of heart valve disease rely on dimensional disease specific measures and are thus unable to capture severity under a concomitant heart valve disease scenario. Experiments were conducted to measure ventricular workload in an inhouse invitro left heart simulator. Inhouse trileaflet heart valves were built and parameterized to model concomitant heart valve disease. Measured ventricular power varied nonlinearly with cardiac output and mean aortic pressure. Significant data collapse could be achieved by the nondimensionalization of ventricular power with cardiac output, fluid density, and a length scale. The dimensionless power, Circulation Energy Dissipation Index (CEDI), indicates that concomitant conditions require a significant increase in the amount of work needed to sustain cardiac function. It predicts severity without the need to quantify individual disease severities. This indicates the need for new fluiddynamics similitude based clinical guidelines to assist patients with multiple heart valve diseases. [Preview Abstract] 

F1.00052: Aortic emboli show surprising size dependent predilection for cerebral arteries: Results from computational fluid dynamics Ian Carr, Robert Schwartz, Shawn Shadden Cardiac emboli can have devastating consequences if they enter the cerebral circulation, and are the most common cause of embolic stroke. Little is known about relationships of embolic origin/density/size to cerebral events; as these relationships are difficult to observe. To better understand stoke risk from cardiac and aortic emboli, we developed a computational model to track emboli from the heart to the brain. Patientspecific models of the human aorta and arteries to the brain were derived from CT angiography from 10 MHIF patients. Blood flow was modeled by the NavierStokes equations using pulsatile inflow at the aortic valve, and physiologic Windkessel models at the outlets. Particulate was injected at the aortic valve and tracked using modified MaxeyRiley equations with a wall collision model. Results demonstrate aortic emboli that entered the cerebral circulation through the carotid or vertebral arteries were localized to specific locations of the proximal aorta. The percentage of released particles embolic to the brain markedly increased with particle size from 0 to $\approx$11.5~mm in all patients. Larger particulate became less likely to traverse the cerebral vessels. These findings are consistent with sparse literature based on transesophageal echo measurements. [Preview Abstract] 

F1.00053: Capture of Magnetic Nanoparticles in Simulated Blood Vessels: Effects of Proteins and Coating with Poly(ethylene glycol) Jaimee Robertson, Christopher Brazel Magnetic nanoparticles (MNPs) have applications in cancer treatment as they can be captured and localized to a diseased site by use of an external magnetic field. After localization, cancer treatments such as magnetically targeted chemotherapy and localized hyperthermia can be applied. Previously, our lab has shown that the percent capture of MNPs is significantly reduced when MNPs are dispersed in protein solutions compared to water or aqueous polymer solutions. The purpose of this study was to determine the effects of proteins on capture efficiency and to investigate the ability of poly(ethylene glycol), PEG, coatings to reduce aggregation of MNPs with proteins, allowing for a greater capture of MNPs in flow. Using Tygon$^{\mbox{{\textregistered}}}$ tubing to simulate blood vessels, a maghemite nanoparticle solution was pumped through a capture zone, where a magnetic field was applied. After passing through the capture zone, the fluid flowed to a spectrophotometer, which measured the absorbance of the solution. The introduction of proteins into the nanoparticle solution reduced the percent capture of MNPs. However, coating the MNPs with PEG aided in preventing aggregation and led to higher capture efficiencies in protein solutions. Additionally, the effects of capture length and protein exposure time were examined. It was found that a higher percent capture is attainable with a longer capture length. Furthermore, on a scale of hours, the percent capture is not affected by the protein exposure time. [Preview Abstract] 

F1.00054: Effect of Varying the Angle of Attack of the Scales on a Biomimetic Shark Skin Model on Embedded Vortex Formation Jennifer Wheelus, Amy Lang, Michael Bradshaw, Emily Jones, Farhana Afroz, Philip Motta, Maria Habegger The skin of fastswimming sharks is proposed to have mechanisms to reduce drag and delay flow separation. The skin of fastswimming and agile sharks is covered with small teethlike denticles on the order of 0.2 mm. The shortfin mako is one of the fastest and most agile ocean predators creating the need to minimize its pressure drag by controlling flow separation. Biological studies of the shortfin mako skin have shown the passive bristling angle of their denticles to exceed 50 degrees in areas on the flank corresponding to the locations likely to experience separation first. It has been shown that for an angle of attack of 90 degrees, vortices form within these cavities and impose a partial slip condition at the surface of the cavity. This experiment focuses on smaller angles of attack for denticle bristling, closer to the range thought to be achieved on real shark skin. A 3D bristled shark skin model with varying angle of attack, embedded below a boundary layer, was used to study the formation of cavity vortices through fluorescent dye visualization and Digital Particle Image Velocimetry (DPIV). The effect of varying angle of attack on vortex formation will be discussed. [Preview Abstract] 

F1.00055: Swimming microrobot powered by stimulisensitive gel Hassan Masoud, Alexander Alexeev Using threedimensional computer simulations, we design a simple maneuverable microswimmer that can selfpropel and navigate in highly viscous (low Reynoldsnumber) environments. Our simple swimmer consists of a cubic gel body which periodically changes volume in response to external stimuli, two rigid rectangular flaps attached to the opposite sides of the gel body, and a flexible steering flap at the front end of the swimmer. The stimulisensitive body undergoes periodic expansions (swelling) and contractions (deswelling) leading to a timeirreversible beating motion of the propulsive flaps that propel the microswimmer. Thus, the responsive gel body acts as an ``engine'' actuating the motion of the swimmer. We examine how the swimming speed depends on the gel and flap properties. We also probe how the swimmer trajectory can be changed using a responsive steering flap whose curvature is controlled by an external stimulus. We show that the turning occurs due to steering flap bending and periodic beating. Furthermore, our simulations reveal that the turning direction can be regulated by changing the intensity of external stimulus. [Preview Abstract] 

F1.00056: Analysis of High Speed Liquid Jets Emitted from Needle Free Jet Injectors Rocco Portaro, AmyLee Gunter, Hoi Dick Ng The replacement of the traditional hypodermic needle by needle free liquid jet injectors has been of great interest to the scientific community over recent years. This study utilizes a specially designed needle free injector in order to describe the behavior of high speed liquid jets. High speed photography is used to depict the injection process, as the jet emitted from the injector penetrates biological tissue. The penetration depth of the jet will be studied by varying parameter such as the jet diameter, geometry and power. This analysis will then be used in improving the performance of liquid free injectors by maintaining more consistent injection depths and minimizing the power required to penetrate human tissue. This in turn leads to painless injections with less risk of contamination and aids in making needle free liquid jet injectors a viable alternative to hypodermic needles. [Preview Abstract] 

F1.00057: An Experimental Study of Flow Separation over a Flat Plate with Transverse Grooves Emily Jones, Amy Lang A shark's scales help to reduce drag over its body by controlling boundary layer separation over its skin. It is theorized that the scales bristle when encountering a reversing flow, thereby trapping vortices between the scales, creating a partial slip condition over the surface and inducing turbulence augmentation in the boundary layer. In an attempt to replicate and study these effects, a spinning cylinder was used in a water tunnel to induce separation over a flat plate with 2 mm, square 2D transverse grooves and sinusoidal grooves of the same size. The results were compared to tripped, turbulent boundary layer separation occurring over a flat plate without grooves using DPIV. The strength of the adverse pressure gradient was varied, and the observed delay in flow separation and other effects upon the boundary layer are discussed. [Preview Abstract] 

F1.00058: Formation of clogs under ultrasound excitation: a microfluidic study Erin Barney, Emilie Dressaire Acoustic waves and more specifically ultrasound are commonly used in microfluidic devices to focus, separate and mix particles. We study the influence of ultrasound on the formation of clogs of colloidal particles in microchannels. In particular we focus on the role played by the flow properties and the characteristics of the acoustic wave (frequency and amplitude). We show that the ultrasound excitation delays the formation of clogs and interpret our results with a simple force balance on the colloidal particle. [Preview Abstract] 

F1.00059: Characterization of Intracellular Streaming and Traction Forces in Migrating Physarum Plasmodia Shun Zhang, Juan C. del Alamo, Robert D. Guy, Juan C. Lasheras Physarum plasmodium is a model organism for cell migration that exhibits fast intracellular streaming. Motile amoeboid physarum plasmodia were obtained from dish cultures of Physarum Polycephalum, a slime mold that inhabits shady cool moist areas in the wild, such as decaying vegetable material. The migrating amoebae were obtained by cutting successively smaller pieces from the growing tips of the cultured parent mold, and their size ranged 0.2 to 0.5 mm. Single amoebae were seeded and let adhere on flexible polyacrilamide gels that were functionalized with collagen, contained 0.2micron fluorescent beads, and were embedded in an aqueous medium. Soon after adhering to the gel, the amoeabe began crawling at about 1mm/hr. Joint timelapse sequences of intracellular streaming and gel deformation were acquired respectively in the bright and fluorescent fields of a confocal microscope at 20X magnification. These images were analyzed using particletracking algorithms, and the traction stresses applied by the amoebae on the surface were computed by solving the elastostatic equation for the gel using the measured bead displacements as boundary conditions. These measurements provide, for the first time, a joint characterization of intracellular mass transport and the forces driving this transport in motile amoeboid cells. [Preview Abstract] 

F1.00060: GENERAL 

F1.00061: Vorticity Flux of LowSpeed Flow Over a Deforming Arc Airfoil Majid Molki, Negin Sattari Vorticity flux generated by a deforming arc airfoil is investigated. The model is based on the finitevolume method for laminar incompressible flow of air over a circulararc airfoil. A deformingmesh approach is employed to accommodate the motion and deformation of the airfoil. The vorticity flux is evaluated at the surface of the airfoil for both nondeforming (rigid) and deforming airfoils. Complex flow features such as boundary layer flows, vortical structures, rolling vortices, and vortex layers are all present and have some degree of influence on the aerodynamic characteristics of the airfoil. It is shown that the vorticity flux at the surface is influenced by tangential pressure gradient and tangential acceleration of the airfoil. Since the pressure gradient and acceleration are nonuniform over the airfoil, their contributions strongly depend on position, and they result in a diffused distribution of vorticity flux magnitude over the surface. Vorticity flux into the fluid results in the formation and growth of vortices which are swept with the flow downstream. [Preview Abstract] 

F1.00062: Unsteady flow around impacting square cylinder Changyoung Choi, Man Yeong Ha, Hyun Sik Yoon The problem on the flow resulting from the collision without rebound of square cylinder with a wall at Re=200 is investigated computationally using the DF/FD method with a finite volume method. Emphasis is on the case of a square cylinder impact by threedimensional numerical simulation, but comparisons with the flow generated by the impact of a circular cylinder are included. A cylindrical body impacting on the wall produces two primary vortex rings. The primary vortex rings spread outward away from the body along the wall. This continues until stalling while lifting induced wall vortices into the primary vortices. For normal square cylinder impact, secondary vortices exhibit a threedimensional instability. Comparison with the circular cylinder impact reveals that this is caused by the differences in flow strength after the cylinder collides with the wall. Oblique square cylinder impacts are also considered. For the oblique square cylinder, a threedimensional instability does not appear in the flow around the cylinder. As the impact angle increases, the wall effect is gradually reduced on one side of the square cylinder. This causes the rollup of the secondary vortex and the increase of the rebound height of the vortex system. [Preview Abstract] 

F1.00063: Density measurements in water using background oriented schlieren technique Shi Qiu, Chuanxi Wang, Veronica Eliasson Undersea earthquakes, tsunamis and underwater explosions are examples of phenomena that cause compressible wave propagation in oceans leading to changes in density and pressure. Here, a direct impact method is used to generate a shock wave in a waterfilled channel and the following changes in the density of the fluid is quantified using an extended background oriented schlieren technique. Background oriented schlieren technique relies on measuring variations in index of refraction in the fluid. A highspeed camera is used to capture multiple frames of the shock wave propagation. A code has been developed to quantify the change in index of refection, and map it to the change in density. Results of density changes due to shock wave propagation in converging waterfilled channels will be presented. [Preview Abstract] 

F1.00064: ThermalStability Characterization of Quantum Dot on Anodized Aluminum as Global Temperature Sensing Hirotaka Sakaue, Akihisa Aikawa Quantum dot (QD) is an attractive chemical as a temperaturesensitive probe for global temperature sensor. It is bright and has a narrow spectrum compared to those of conventional temperaturesensitive probes. Previous studies show that QD on anodizedaluminum support is applied to high temperature measurement (above 400 K) in hypersonic flows. However, it is also reported that QD is not stable at this temperature range. To answer to the stability issue, we characterize a thermal stability of a QD on anodizedaluminum support. The luminescence from the resultant sensor is measured in the temperature range of 100 to 475 K and the time range of 0 to 1000 s. It is shown that the thermal stability is hold below 298 K. Above 315 K, a sudden decrease and a recovery of the luminescence are measured. It is found that the amount of decrease is proportional to the temperature. The maximum decrease in the intensity is 89{\%} at 475 K after 1000 s. At 315 K, the intensity is recovered to the initial amount after 1000 s. [Preview Abstract] 

F1.00065: Effect of PTFE Particle on SuperHydrophobic Coating for AntiIcing Riho Kamada, Katsuaki Morita, Koji Okamoto, Akihito Aoki, Shigeo Kimura, Hirotaka Sakaue Anti/deicing of an aircraft is necessary for a safe flight operation. Mechanical processes, such as heating and deicer boot, are widely used. Deicing fluids should be coated every time before the takeoff, since the fluids come off from the aircraft while cruising. We study a superhydrophobic coating as antiicing for an aircraft. It is designed to coat the aircraft without removal. Since a superhydrophobic surface prevents water by reducing the surface energy, it would be another way to prevent ice on the aircraft. We provide a temperaturecontrolled room, which can control its temperature at the icing conditions (14 to 0 degrees C). The contact and sliding angles are measured to study the effect of the various PTFE particles on the superhydrophobic coatings for antiicing. The particle diameter is varied from 5 to 30 micrometer. Comparisons among the superhydrophobic coatings by various PTFE particles are made to discuss the performance of the resultant coatings as antiicer. [Preview Abstract] 

F1.00066: Design patterns for training fluid dynamics experimentalists Randall Tagg What practical knowledge would your ideal lab student, technician or even postdoc possess? Borrowing the idea of design patterns from the fields of architecture and computer science, we claim that there are technical problems common to many investigations with oftenused design solutions. These would form a useful repertoire that thoughtful practitioners can adapt. Creatively breaking the rules is also encouraged. We invite other ideas for fluid experiment design patterns towards the end of creating a webbased resource that helps new experimentalists get up to speed quickly. We are creating such a resource so that it also serves precollege students invited into research experiences and inventive citizen scientists exploring new technologies. [Preview Abstract] 

F1.00067: ABSTRACT WITHDRAWN 

F1.00068: ABSTRACT WITHDRAWN 

F1.00069: Dynamics of spheroid particles in channel flow Wenbin Mao, Alexander Alexeev The effect of inertia on the dynamics of rigid spheroid microparticles in a pressuredriven channel flow is studied using a hybrid lattice Boltzmann and lattice spring method. We find distinctive behaviors of particles depending on the particle shape, initial orientation, and ratio of particle size to the channel size. Two possible stable modes of motion are found for prolate spheroids. Particles either tumble in a shear plane or spin with the axis parallel to the vortex direction. We present a phase diagram showing the transition between these two modes. Crossstream migration and equilibrium trajectories of particles are also investigated and found to depend on the particle shape and mode of motion. The simulations results are compared with experimental data showing favorable agreement. Our results will be useful for separating biological and synthetic particles by size and shape. [Preview Abstract] 

F1.00070: TwoDimensional ParticleinCell Simulation of Cylindrical Magnetron Sputters for the Improvement of Target Utilization Hur MinYoung, Bae HownWon, Lee HoJun, Lee HaeJun Magnetron sputtering has been commonly used for the deposition of a wide range of industrial thin film coating. This method has almost no restrictions in the target materials and the magnetic field enables lower pressures operation. Conventional flat type sputters generate ionbombardment sputtering in only a localized region of target where electric fields and magnetic fields are perpendicular to each other. Therefore, the utilization efficiency of the target material is about 20$\sim$30\%. To overcome this drawback, a rotating cylindrical target is devised to make uniform sputtering on the target. In this paper, the difference of the physical effects of ions on the targets between the flattype and the cylindricaltype sputters is investigated using a twodimensional particleincell simulation with Monte Carlo collisions. Especially for the calculation of cylindrical field solver with a finite difference method, an image charge method is introduced instead of solving the Poisson equation. Simulation Diagnostics include the plasma density, the distributions of energy and angle of incident ions on the target, and the deposition profiles on the substrate calculated by a raytrace particle deposition model. The analysis for the rotating speed and the magnet structure is to be discussed. [Preview Abstract] 

F1.00071: Eulerian and Lagrangian Analysis of a Simulated unsteady Flow Behind a Circular cylinder Keith Holmes, Melissa Green The unsteady wake behind a circular cylinder is numerically simulated and analyzed utilizing various Eulerian methods and the Lagrangian finitetime Lyapunov exponent (FTLE). The objective is to identify and distinguish among shed vortices in the wake, and particular attention is given to the near wake immediately downstream of the cylinder. The Eulerian methods capably determine regions of the flow associated with greatest magnitude of vorticity in the near wake, as has been shown previously. Ridges of the FTLE field are able to objectively identify structures in the near wake by outlining the boundaries between vortices. This includes boundaries among structures of the same sign, a distinction not possible using the Eulerian methods. The formation of these boundaries help to distinguish between structures still developing around the cylinder surface and those that have been shed from the cylinder. [Preview Abstract] 

F1.00072: Physics Based Compressive Sensing Approach Applied to Airfoil Data Collection and Analysis Zhe Bai, Thakshila Wimalajeewa, Zachary Berger, Mark Glauser, Pramod Varshney, Donald Leskiw Compressive Sensing (CS), a newly developing method in signal processing, was used in physics to estimate a twodimensional, high Reynolds number turbulence flow velocity field over a NACA4412 airfoil. The facility and experimental setup in the wind tunnel were introduced, from which the velocity data was obtained. The principle of CS and its feasibility applied to the physical velocity field was demonstrated and Discrete Cosine Transform (DCT) was used to attain the sparsity. The reconstructed velocity field was provided to compare with the experimental measurement of the PIV setup and the normalized MSE between the original velocity filed and the reconstructed one was calculated for a number of snapshots, with the comparison of snapshot POD method. Also, a joint CS and POD technique was discussed, in which snapshot POD was used as a basis to find transformations that sparsify the data for CS to retrieve. The fusion of several snapshots was discussed by doing the before and after the CS process. The effectiveness of CS used for the approximation of large and distributed airfoil data sets through a small number of samples collection was demonstrated, which could also be expected to be readily applied to other types of datasets. [Preview Abstract] 

F1.00073: Simulations of bubblewall collision and bouncing Sohrab Towfighi, Hadi Mehrabian, Roberto Zenit, James J. Feng The collision of a rising bubble with a hydrophilic upper wall is studied numerically using an axisymmetric phasefield model. Prior experiments show bubble bouncing or adhesion depending on its incoming velocity. Using experimental parameters, our computation reproduces these different behaviors, including bubble breakup, arrest, and rebound. In particular, dimples are observed on both the fore and aft sides. We further investigate the scaling of the coefficient of restitution and the critical condition delineating arrest from rebound. The latter is plotted as a phase diagram in terms of the Ohnesorge and Weber numbers. [Preview Abstract] 

F1.00074: Laminar separation bubble formation using a circular cylinder rotating adjacent to a flat plate Farhana Afroz, Amy Lang, Emily Jones, Michael Bradshaw A new method for the formation of a laminar separation bubble (LSB) on a flat plate was investigated whereby an adverse pressure gradient (APG) was induced by the presence of a rotating cylinder. A parametric study was performed where the rotation rate and gap height (G) was changed to vary the strength of APG which affects the nature and extent of the LSB. Results showed that the height (H), length (L) and the separation point (S) of the LSB varied in conjunction with the strength of the APG and the Re. TimeResolved Digital Particle Image Velocimetry (TRDPIV) was used to document the LSB in this water tunnel study. Results captured the effects of changing flow speed, cylinder location and rotation rate on the development of the LSB. [Preview Abstract] 

F1.00075: Selective interaction between microbubbles and modulating waves in a TaylorCouette flow Tomoaki Watamura, Yuji Tasaka, Yuichi Murai Modifications of a coherent vortical structure by dispersed microbubbles have been investigated in a vertical TaylorCouette flow, which is the flow generated between coaxialrotating double cylinders. Radii of the inner and outer cylinders are 95 mm and 105 mm, respectively. The radius ratio and aspect ratio are 0.905 and 20, respectively. Flow mode in the experiments represents wavy vortex flow and modulated wavy vortex flow. Hydrogen bubbles with 60 $\mu $m in the mean diameter were generated by water electrolysis and dispersed from a platinumwire electrode mounted at the bottom of the fluid layer. Maximum void fraction estimated by input power is smaller than 0.01{\%}. Velocity distribution of microbubbles in a Taylor vortex array is determined by image analysis, and show preferential distribution and motion in the oscillating vortex tube. The fluctuation power of the basic wave was increased by adding microbubbles, while the power of its modulation was decreased. The gradient of the azimuthal velocity in the radial direction, i.e. origin of skin frictional drag acting on the cylinder walls, was decreased. These modifications of flow structure represent the suppression of the flow transition, due to the excitation of the basic wave oscillation and increase of momentum transfer by bubble swarm. [Preview Abstract] 

F1.00076: Wave localization of linear gravity waves in shallow water: Global measurements and agreement between random matrix theory and experiments Andrea Schmessane Wave localization explains how a perturbation is trapped by the randomness present in a propagation medium. As it propagates, the localized wave amplitude decreases strongly by multiple internal reflections with randomly positioned scatterers, effectively trapping the perturbation inside the random region. The characteristic length where a localized wave is propagated before being extinguish by randomness is called localization length. We carried experiments in a quasionedimensional channel with random bottom in a shallow water regime for surface gravity water waves, using a Perfilometry Fourier Transform method, which enables us to obtain global surface measurements. We discuss keys aspects of the control of variables, the experimental setup and the implementation of the measurement method. Thus, we can control, measure and evaluate fundamental variables present in the localization phenomenon such as the type of randomness, scattering intensity and sample length, which allows us to characterize wave localization. We use the scattering matrix method to compare the experimental measurements with theoretical and numerical predictions, using the Lyapunov exponent of the scattering matrix, and discuss their agreement. [Preview Abstract] 

F1.00077: STABILITY 

F1.00078: The effect of a magnetic field on vortex breakdown in an enclosed swirling flow Yang Yu, Benwen Li, Andre Thess An axisymmetric swirling flow, which is driven by rotation of top lid of an enclosed cylinder and subjected to of an axial uniform magnetic field, is studied numerically. As Reynolds numbers increasing, the phenomenon of vortex breakdown, a vortex appears and disappear on the axis of the cylinder, is a significantly process in the transition from the laminar flow to turbulent flow. The collocation spectral solver is developed to simulate the MHD flow. While, different conductivities of the walls, insulating and perfectly conducting cases, are considered to analyze the magnetic effect on the vortex breakdown. In order to validate the collocation spectral solver, the dynamic and MHD problems are referred, respectively. In the presence of an axial uniform magnetic field, the effects on the nondimensional lengths of vortex along the zaxis and the central positions of vortex on the zaxis are presented, and the influence of the conductivities of the top lid, bottom base and side wall are discussed. The results show that, for different electrical boundary conditions, the behaviors of vortex are significantly different and even converse. In particular, when the top rotating lid is the only perfectly conducting, the magnetic effects are the strongest. [Preview Abstract] 

F1.00079: Threedimensional Instability in the Wake of an Angulated Cylinder KyungSoo Yang, ChoonBum Choi Floquet stability analysis has been carried out to detect the onset of 3D instability in the laminar flow past a 2D angulated cylinder. The shape of the cylinder crosssection considered here includes a normal flat plate up to a square cylinder as the aspect ratio (\textit{AR}) varies. As \textit{AR} decreases, mode B and mode QP vanish and mode A2 and mode QP2 emerge. These modes were not observed in the case of flow past a square cylinder. In a finite range of \textit{AR}, mode A instability becomes unstable and then returns to be stable again as Re increases. This distinctive phenomenon can be identified by a closed curve in the neutral stability diagram. Threedimensional simulations of some selected cases were performed for validation, showing good agreement with the current Floquet stability analysis. We also present contours of the streamwise vorticity component obtained from the Floquet analysis, and Q contours based on the DNS to elucidate the 3D vortical structures of the 3D modes Our results shed light on a complete understanding of the onset of 3D instability in the presence of an angulated cylinder [Preview Abstract] 

F1.00080: Experimental Investigation of RichtmyerMeshkov Instability on Inclined Interface Chris McDonald, Jacob McFarland, David Reiley, Brian Reid, Devesh Ranjan Results are presented from our recent experiments studying shock wave interaction with an inclined interface between two different fluids performed in a new newly built Texas A{\&}M variable inclination shock tube facility. The variable inclination capability of the shock tube allows for an inclined interface to be created with ease, without changing the Mach number (pressure gradient) or Atwood number (density gradient). The ease of creating the interface provides a clean and repeatable interface for studying the RichtmyerMeshkov Instability problem. The results presented from our initial experiments are from a Mach 1.6 shock wave interaction with a nitrogeninfusedfogovercarbon dioxide interface for an inclination angle of 60 degrees. Quantitative results gathered from these experiments such as the mixing width growth rate, and vorticity deposition will be discussed in detail. Numerical simulations of the experiments are performed using the ARES code (LLNL) and the time evolution of the interface width, measured empirically, is compared to the corresponding numerical predictions. [Preview Abstract] 

F1.00081: Spatiotemporal spectral analysis of a forced cylinder wake Juan D'Adamo, Ramiro GodoyDiana, Jos\'e Eduardo Wesfreid The wake of a circular cylinder performing rotary oscillations is studied using hydrodynamic tunnel experiments at $Re=100$. Twodimensional particle image velocimetry on the midplane perpendicular to the axis of cylinder is used to characterize the spatial development of the flow and its stability properties. The lockin phenomenon that determines the boundaries between regions of the forcing parameter space were the wake is globally unstable or convectively unstable is scrutinized using this experimental data. A novel method based on the analysis of power density spectra of the flow allows us to give a detailed description of the forced wake, shedding light on the energy distribution in the different frequency components and in particular on a cascadelike mechanism evidenced for a high amplitude of the forcing oscillation. In addition, a calculation of the drag from the velocity field is performed, allowing us to relate the resulting force on the body to the wake properties. Reference: Phys. Rev. E 84, 056308 (2011). [Preview Abstract] 

F1.00082: Analysis of G\"ortler Vortices Spanwise Wavelenght Influence in Heat Transfer Rates Leandro F. Souza, Vinicius Malatesta, Joseph T.C. Liu The centrifugal instability mechanism in boundary layers flows over concave surfaces is responsible for the development of streamwise counterrotating vortices, known as G\"ortler vortices. These Vortices create two regions in the spanwise direction, the upwash and downwash regions. The downwash region is responsible to compress the boundary layer towards the wall, increasing drag and heat transfer rates. The upwash region does the opposite. In the nonlinear development of the G\"ortler vortices the upwash region becomes narrow, and the average drag and heat transfer rate is higher than that for a Blasius boundary layer. In the present research, using a Spatial Direct Numerical Simulation, it is analyzed the influence of the G\"ortler Vortices spanwise wavelength in heat transfer rates. Different wavelengths are analyzed and compared with experiments.\footnote {L. Momayez, P. Dupont and H. Peerhossaini, Int J Therm Sci, 43, 753760 (2004)} The results show that steady G\"ortler flow can reach heat transfer rates higher than the turbulent values, even without introducing secondary instabilities. [Preview Abstract] 

F1.00083: Flow Control Characterization of~PIV Flow Field Using POD Matthew Berry, Zach Berger, Kerwin Low, Alexis Zelenyak, Sivaram Gogineni, Mark Glauser The main focus of this experiment is on the analysis and flow control of a high speed jet, with a nozzle diameter 2''. The flow field was investigated at Mach 0.6 using twocomponent large window PIV. The velocity was examined in the streamwise direction of the rz plane with a window size of about 6 diameters. A glove fitted with 8 synthetic actuators was attached and arranged azimuthally around the lip of the jet. A signal was driven through the actuation system causing the glove to inject flow into the jet field in an attempt to clean up the jets shear layer. Sensors were set up in order to sample the near field pressure measurements and the far field acoustics simultaneously with the PIV. Lowdimensional modelling was performed on the gloves actuation system running alone; without the high speed jet. Proper orthogonal decomposition was performed at the lip of the jet, in order to observe the high energy structures of the actuation glove. Previous work shows that the first mode consists of 15{\%} of the total energy, while the first 9 modes are responsible for approximately 40{\%} of the total energy. Combing the PIV information with a complete hotwire velocity profile, we can gain a better understanding of how the closed loop control system is affecting the jets flow field. [Preview Abstract] 

F1.00084: Magnetic resonance imaging study of RayleighBenard convection in near and supercritical hexafluoroethane Joshua M. Bray, Sarah L. Codd, Joseph D. Seymour RayleighBenard convection (RBC) has been extensively studied; however, the regime of temperature and pressure above the critical point (Tc, Pc) remains largely unexplored experimentally. In this regime, convection modes are sensitive to divergence in various transport properties, providing a unique model system for many geophysical flows and allowing access to high Rayleigh numbers $Ra$, of order 10$^{13}$. We present magnetic resonance imaging (MRI) analysis of RBC in a supercritical fluid. Spatially resolved velocity images and ensembleaveraged transport dynamics were acquired noninvasively for C$_2$F$_6$ (Tc = 20 C, Pc = 31 bar) in a low aspect ratio chamber at pressures 32 bar and 70 bar with and without a 2.5 C temperature gradient. With no applied gradient, within the temperature control resolution of +/0.1 C, convection at 70 bar is minimal, but is rapid at 32 bar due to nearcritical density divergence. The velocity profile is concentric, in contrast to a single convective cell in noncritical fluids. An applied temperature gradient produced turbulent flow, destabilizing the concentric velocity distribution at 70 bar and generating incoherent fluid motion at 32 bar. Near and supercritical fluids provide a model system for tuning fluid dynamics through thermodynamics. [Preview Abstract] 

F1.00085: Using Lyapunov Vectors to Quantify Spatiotemporal Chaos in RayleighBenard Convection Mu Xu, Alireza Karimi, Jeffrey Tithof, Miro Kramar, Vidit Nanda, Michael Schatz, Konstantin Mischaikow, Mark Paul Spatiotemporal chaos is a common feature of spatiallyextended systems that are driven farfromequilibrium with examples that include the dynamics of the weather and climate, fluid turbulence, and excitable media. Despite significant effort, many open questions remain regarding our physical understanding of highdimensional chaotic systems such as these. Using recent advances in computing algorithms and available supercomputing resources it is now possible to compute the spectrum of Lyapunov exponents and orthonormal Lyapunov vectors for experimental conditions. We present largescale parallel numerical simulations of RayleighBenard convection undergoing spiral defect chaos for very long times and for laboratory conditions that we compare with experiment. We use averages of the leading order orthonormal Lyapunov vector to gain insight into the regions in space generating the most disorder which we compare with experimentally accessible quantities. We discuss the similarities and differences between characteristic and orthonormal Lyapunov vectors. Lastly, we describe our efforts to compute the characteristic Lyapunov vectors for RayleighBenard convection. [Preview Abstract] 

F1.00086: Penetrative convection induced by a statically unstable density distribution in a very thin central layer Rishad Shahmurov, Layachi Hadji Several models of penetrative convection have been studied (Gribov $\&$ Gurevich, 1957; Veronis, 1963; Matthews, 1988; Batchelor $\&$ Nitsche, 1990; Simitev $\&$ Busse, 2010). We consider RayleighB\'{e}nard convection with a static density distribution that has a piecewise linear dependence on the vertical coordinate and whose unstably stratified part occupies a central layer of thickness $\epsilon \ll 1$. Some limiting cases corresponding to the linear eigenvalue problem are treated analytically and the results confirmed by a detailed numerical investigation. Steady twodimensional flow patterns are determined numerically for supercritical Rayleigh numbers in the range $\epsilon \ge 0.06$. For $0.2 \le \epsilon \le 0.5$, an analytical nonlinear stability threedimensional study is undertaken in the case of poorly conducting boundaries. A weakly nonlinear evolution equation for the leading order temperature perturbation is also derived and solved numerically as function of $\epsilon$ and Prandtl number. The effect of the boundaries on the flow characteristics diminishes as $\epsilon \rightarrow 0$, leading us to study the stability of an unbounded stratified fluid for which similarity type solutions are obtained. Our findings are compared to those of the models mentioned above. [Preview Abstract] 

F1.00087: Investigation of instability of displacement front in nonisothermal flow problems Natalia Syulyukina, Anna Pergament In this paper, we investigate the issues of front instability arising in nonisothermal flow displacement processes. The problem of twophase flow of immiscible fluids, oil and water, is considered, including sources and dependence of viscosity on temperature. Threedimensional problem with perturbation close to the injection well was considered to find the characteristic scale of the instability. As a result of numerical calculations, theoretical studies on the development of the instability due to the fact that the viscosity of the displacing fluid is less than the viscosity of the displaced have been confirmed. The influence of temperature on the evolution of the instability was considered. For this purpose, the dependence of oil viscosity on temperature has been added to the problem. Numerical calculations were carried out for different values of temperature and it was shown that with increasing of production rate. Thus, it has been demonstrated that the selection of the optimal temperature for injected fluids a possible way for stimulation of oil production also delaying the field waterflooding. [Preview Abstract] 

F1.00088: Understanding the impact of initial condition on low Atwood number RayleighTaylor driven flows Sarat Chandra Kuchibhatla, Devesh Ranjan Experimental investigation of the effects of initial conditions on RayleighTaylor instability was performed using the Water Channel facility at Texas A{\&}M University. Hot and cold water (with a temperature difference of $\sim $78 degrees C) selected as working fluids were unstably stratified using a splitter plate resulting in a low Atwood number of $\sim $0.0015. Using a servo controlled flapper system the effect of initial conditions is studied using different diagnostics such as optical imaging, thermocouples and hotwire anemometry. A parametric study comprising of up to 10 modes of the initial condition was performed by varying the number of modes as well as modal composition ($i.e.$ ratio of wavenumbers and phase differences). Variation of density, temperature and velocity field in the linear and nonlinear stages of RT growth was recorded and analyzed. At nondimensional time, $t^{\ast}=t(A_{t}g$/H)$^{0.5}$= 1.3, where $t$ is the time, $H$ is the width of the Channel, and $g$ is the acceleration due to gravity, power spectra of the nondimensional density showed finescale components that are dependent upon the initial condition. Plots of scalar dissipation and mixing rate indicate greater dissipation rate at early times that tends to asymptote to the order of kinematic viscosity at late times. [Preview Abstract] 

F1.00089: Miscible and immiscible experiments on the RayleighTaylor instability using simultaneous planar laser induced fluorescence and backlight visualization. Matthew Mokler, Michael Roberts, Jeffrey Jacobs Incompressible RayleighTaylor instability experiments are presented in which two stratified liquids having Atwood number of 0.2 are accelerated in a vertical linear induction motor driven drop tower. A test sled having only vertical freedom of motion contains the experiment tank and visualization equipment. The sled is positioned at the top of the tower within the linear motors and accelerated downward causing the initially stable interface to be unstable and allowing the RayleighTaylor instability to develop. Experiments are presented with and without forced initial perturbations produced by vertically oscillating the test sled prior to the start of acceleration. Half of the experimental tank is visualized using a 445nm laser light source that illuminates a fluorescent dye mixed in one of the fluids. The other half is illuminated with a white backlight. The resulting images are recorded using a monochromatic high speed video camera allowing for the measurement of spike and bubble mixing layer growth rates for both visualization techniques in a single experiment. [Preview Abstract] 

F1.00090: Simulations of MHD Instabilities in Protoplanetary Disks Ezekiel Hadley, Joseph Barranco We have developed a 3D spectral, anelastic, magnetohydrodynamic code for rapidly rotating, strongly sheared, stratified protoplanetary disks. The Cartesian domain is resolved with a FourierFourierChebyshev basis, and uses horizontal coordinates that advect with the background shear. With this tool, we simulate the magnetorotational instability at high resolution and investigate the development of MHD turbulence. [Preview Abstract] 

F1.00091: TURBULENCE 

F1.00092: Passive and active transport in a chaotic flow field Christopher Mehrvarzi, Mark Paul The transport of a scalar species in a complex flow field is important in many areas of current interest such as the combustion of premixed gases, the dynamics of particles in the atmosphere and oceans, and the reaction of chemicals in a mixture. There has been significant progress in understanding transport in steady periodic flows such as a ring of vortices. In addition, transport in turbulent flow has an extensive literature. However, in this work, we focus upon the transport of a scalar species in a threedimensional timedependent flow field given by the spiral defect chaos state of RayleighBenard convection (the buoyant convection that results when a shallow fluid layer is heated from below). We take advantage of the significant theoretical and numerical progress in recent years that provides a physical understanding of this chaotic flow field. We study the transport using a highly efficient and parallel spectral element approach to simultaneously evolve the Boussinesq and reactionadvectiondiffusion equations in large cylindrical domains with experimentally relevant boundary conditions. For active transport we include a reaction term with relevance to the combustion of premixed gases that are undergoing chaotic convection. We develop and use diagnostic tools to quantify the transport over a wide range of parameters in order to gain new physical insights. [Preview Abstract] 

F1.00093: Turbulent Heat Transfer in Ribbed Pipe Flow Changwoo Kang, KyungSoo Yang From the view point of heat transfer control, surface roughness is one of the popular ways adopted for enhancing heat transfer in turbulent pipe flow. Such a surface roughness is often modeled with a rib. In the current investigation, Large Eddy Simulation has been performed for turbulent flow in a pipe with periodicallymounted ribs at \textit{Re}$_{\tau }$=700, \textit{Pr}=0.71, and $p/k$=2, 4, and 8. Here, $p$ and $k$ represent the pitch and rib height, respectively. The rib height is fixed as one tenth of the pipe radius. The profiles of mean velocity components, mean temperature, rootmeansquares (rms) of temperature fluctuation are presented at the selected streamwise locations. In comparison with the smoothpipe case at the same \textit{Re} and \textit{Pr}, the effects of the ribs are clearly identified, leading to overall enhancement of turbulent heat transfer in terms of \textit{Nu}. The budget of temperature variance is presented in the form of contours. The results of an Octant analysis are also given to elucidate the dominant events. Our LES results shed light on a complete understanding of the heattransfer mechanisms in turbulent ribbedpipe flow which has numerous applications in engineering. [Preview Abstract] 

F1.00094: Experimental Analysis of Coherent Structures in the Unsteady Wake of a Circular Cylinder Jacob Morrida An experimental analysis of the twodimensional unsteady wake behind a circular cylinder was studied at a range of Reynolds number, and the data was compared with numerical results. The near wake region was analyzed to better understand the evolution of coherent structures, in pursuit of effective control over when and where vortex shedding occurs. For the experiments, a DPIV measurement system was used to collect twodimensional velocity data. The properties of the wake were determined by Eulerian vortex criteria and Lagrangian coherent structures. Using these methods of analysis, the regions of flow separation and vortex shedding were closely observed to discover when and where the separation occurred. Of particular interest was whether identification of this shedding using the two forms of analysis differed between the experimental and numerical results. The ultimate goal is to objectively identify the shedding phenomenon as a target for flow control in future applications. [Preview Abstract] 

F1.00095: Geostrophic balance and the emergence of helicity in rotating stratified turbulence Raffaele Marino, Pablo D. Mininni, Duane Rosenberg, Annick Pouquet We perform numerical simulations of decaying rotating stratified turbulence and show, in the Boussinesq framework, that helicity (velocityvorticity correlation), as observed in supercell storms and hurricanes, is created due to geostrophic balance common to largescale atmospheric and oceanic flows. Helicity emerges from the joint action of eddies and of inertial and gravity waves of respective frequencies $f$ and $N$, and it occurs when the waves are sufficiently strong, with $N/f < 3$. Outside this regime, and up to the highest Reynolds number obtained in this study, namely $Re\approx 10^4$, helicity production is found to be persistent for $N/f$ as large as $\sim 17$. [Preview Abstract] 

F1.00096: Development and assessment of dynamic watersurface roughness model for largeeddy simulation of winds blowing over water waves Lian Shen, Di Yang, Charles Meneveau Largeeddy simulation (LES) has become a useful tool for the study of turbulent winds blowing over water surfaces. The surfaces are usually covered by waves with various lengths, interacting with the wind turbulence over a wide range of scales. In the LES, in addition to the subgridscale (SGS) stress in the flow, the SGS surface roughness also needs to be modeled. In this study, following the work by Anderson and Meneveau (JFM, 2010) on the dynamic modeling of the SGS roughness of stationary surfaces, we have developed a new dynamic model for the watersurface SGS roughness based on the physics of surface waves. The roughness is quantified by an integral of the SGS wave spectrum weighted based on the windwave kinematics, with an unknown model coefficient as prefactor. This coefficient is determined dynamically based on the firstprinciples constraint that the total surface drag force must be independent of the LES filter scale. This new roughness model is assessed by \textit{a priori} and \textit{a posteriori} tests, and is found to successfully capture the effects of SGS surface waves on the wind turbulence without \textit{ad hoc} prescription of model parameters. [Preview Abstract] 

F1.00097: Generation of hairpin vortex packet in channel flow at $Re_\tau \le 590$ Kyoungyoun Kim The generation of hairpin vortex packet from an initial single vortex is examined by direct numerical simulation for channel flows at $Re_\tau$ = 180, 395, and 590. The initial vortex structure is given by conditionally averaged flow field with the Q2 event specified at $y^+=50$ in fully developed turbulent channel flow. The vortex packet formation in higher Reynolds number flows is very similar to that in $Re_\tau$ =180 reported by Zhou \textit{et al.} (1999, J. Fluid Mech.); the initial vortex is developed to a primary hairpin vortex (PHV) and the secondary hairpin vortex is generated upstream of PHV. As time proceeds, the vortices move downstream with almost the same convection velocity and little dispersion, forming a vortex packet. Comparison of the packet formation for different $Re_\tau$ reveals that the secondary hairpin vortex is generated with time scales based on the wall units. At the time when the head of PHV has grown to the channel center, the inclination angle of the vortex packet is approximately $12 \sim 14^{\circ}$ which is insensitive to $Re_\tau$, consistently with linear stochastic estimation results with PIV measurement by Christensen \& Adrian (2001, J. Fluid Mech.). [Preview Abstract] 

F1.00098: Effect of Seeding Particles on the Shock Structure of a Supersonic Jet David Porta, Carlos Echeverr\'Ia, Catalina Stern The original goal of our work was to measure. With PIV, the velocity field of a supersonic flow produced by the discharge of air through a 4mm cylindrical nozzle. The results were superposed to a shadowgraph and combined with previous density measurements made with a Rayleigh scattering technique. The idea was to see if there were any changes in the flow field, close to the high density areas near the shocks. Shadowgraphs were made with and without seeding particles, (spheres of titanium dioxide). Surprisingly, it was observed that the flow structure with particles was shifted in the direction opposite to the flow with respect to the flow structure obtained without seeds. This result might contradict the belief that the seeding particles do not affect the flow and that the speed of the seeds correspond to the local speed of the flow. [Preview Abstract] 

F1.00099: Calibration of Discrete Random Walk (DRW) Model via G.I Taylor's Dispersion Theory Teymour Javaherchi, Alberto Aliseda Prediction of particle dispersion in turbulent flows is still an important challenge with many applications to environmental, as well as industrial, fluid mechanics. Several models of dispersion have been developed to predict particle trajectories and their relative velocities, in combination with a RANSbased simulation of the background flow. The interaction of the particles with the velocity fluctuations at different turbulent scales represents a significant difficulty in generalizing the models to the wide range of flows where they are used. We focus our attention on the Discrete Random Walk (DRW) model applied to flow in a channel, particularly to the selection of eddies lifetimes as realizations of a Poisson distribution with a mean value proportional to $\kappa/\epsilon$. We present a general method to determine the constant of this proportionality by matching the DRW model dispersion predictions for fluid element and particle dispersion to G.I Taylor's classical dispersion theory. This model parameter is critical to the magnitude of predicted dispersion. A case study of its influence on sedimentation of suspended particles in a tidal channel with an array of Marine Hydrokinetic (MHK) turbines highlights the dependency of results on this time scale parameter. [Preview Abstract] 

F1.00100: A Comparative Study of Spatially Evolving SelfPropelled Wakes and a Patch of Turbulence in a Stratified Fluid Anikesh Pal, Matthew de Stadler, Sutanu Sarkar Direct numerical simulation (DNS) is used to compare the evolution of a selfpropelled wake and a patch of turbulence in a stratified fluid. The primary focus of this study is to determine the influence of the mean velocity profile on the evolution of the wake. The cases considered are: (a) selfpropelled wake with a canonical mean velocity profile, (b) selfpropelled wake with the mean removed, (c) a patch of turbulence with the same initial energy spectrum, and (d) a patch of turbulence with a different initial energy spectrum. The Reynolds number (Re), Froude number (Fr) and Prandtl number (Pr) used in the simulations are 10000, 3.194 and 1 respectively. Auxiliary temporally evolving simulations are used to generate the inlet boundary conditions for the spatially evolving cases. We obtain qualitatively and quantitatively similar results among (a), (b) and (c) for the evolution of kinetic energy, vortical structures and the wave field. However the wake dynamics in case (d) with a different initial energy spectrum show significant differences. The implication is that the fluctuating components of the velocities close to a body determine the subsequent flow. The mean velocity may exert an indirect influence through its influence on the nearwake turbulence spectrum. [Preview Abstract] 

F1.00101: Volumetric Lattice Boltzmann Simulation for Fluid dynamics and Turbulence in Practical Syringes Everton Lima, Debanjan Deep, Huidan (Whitney) Yu We conduct numerical experiments to study fluid dynamics and turbulence in syringes using volumetric lattice Boltzmann method (VLBM) that is developed for dealing with arbitrary moving boundaries. Several common used medical syringes are used to predict the efficiency and safety of syringes experiencing low flow infusion rates. It is found that smaller size syringes reach a steady flow rate much sooner than larger ones, which are in quantitative agreement with experimental results. The relation between the syringe size and its steady flow rate is revealed. At low flow rates, corner vortices are observed. We explore conditions that lead to turbulent flow aiming to aid safer syringe application in nursing practices. [Preview Abstract] 

F1.00102: 10kHz TRPIV nearfield velocity and farfield noise: experimental results of a Mach 0.6 jet Pinqing Kan, Jacques Lewalle Last year, we extracted footprints of sources from farfield pressure data of high speed jet. In this paper, we focus on processing 10kHz TRPIV data in the nearfield region. The velocity and pressure data were collected in the jet experiment of Kerwin Low, et al in 2011. From the PIV snapshots, we extract kinematic indicators, construct their histories over the sequence of snapshots, and select the most promising diagnostics by crosscorrelation with farfield pressure. For these indicators, including mass flux, we map out their fluctuations and their downstream propagation. In particular, the phase velocity of fluctuations is compared to the local convective speed. Events with large relative phase velocity are identified, and the corresponding velocity and vorticity fields are mapped out. Our goal is to correlate such events to the farfield footprints of sources. For more info and results related to the experiment, please refer to abstracts by Z.P. Berger and by M.G. Berry at this meeting. This work is supported by Glauser group of Syracuse University, Spectral Energies LLC under AFOSR SBIR grant, and by a Syracuse University Graduate Fellowship. [Preview Abstract] 

F1.00103: Comparison of 10kHz TRPIV and LES nearfield data in high speed jets Jacques Lewalle, Pinqing Kan The identification of the sources of noise in highspeed jets may help formulate control strategies, an important unsolved problem. We report on the existence of large intermittent and localized relative phase velocities for nearjet fluctuations, and on the flow patterns that are associated with them (see companion abstract by P. Kan). Here we analyze two data sets. Experimentally, 10 kHz TRPIV in a $Ma=0.6$ cold jet (Re = 700,000) yielded two components of velocity, from which we calculate the phase velocities for various indicators (see related abstracts by Z.P. Berger and by M.G. Berry; data provided by Spectral Energies LLC). Similar results are obtained for Ma=0.9 LES results (Re = 400,000, sampling at 80 kHz). The comparison of algorithms and flow patterns vindicates our approach. Correlations with farfield events will also be attempted. Thanks to Guillaume Daviller (Institut PPrime, France) for the LES data, and to the Glauser group at Syracuse University. [Preview Abstract] 

F1.00104: An experimental study of the turbulent development of RichtmyerMeshkov instability with a random initial perturbation Vladimer Tsiklashvili, Oleg Lokhatchev, Jeffrey Jacobs RichtmyerMeshkov (RM) instability is studied in a vertical shock tube experiment. The instability is observed between two gases of different densities accelerated by an incident planar shock wave. The stable stratification of the gases is created by introducing air seeded with smoke through a plenum at the top of the driven section, and SF6 through a plenum at the bottom. The gases are oscillated vertically using two loud speakers, located at the top and bottom of the driven section. Faraday waves created on the interface of the two gases results in a random initial perturbation from which the RM instability develops. The current study focuses on the development of the turbulent mixing layer width following the shockinterface interaction. In past experiments, a variety of growth behaviors has been observed. In some experiments the mixing layer width initially grows rapidly and then saturates later on. Other experiments have more gradual, almost linear growth behavior. In the new experiments views of the initial perturbation are captured along with the growth behavior in order to determine the effects of initial conditions on the mixing layers width's development. [Preview Abstract] 

F1.00105: Fluid dynamics at transition regions of enhanced heat transfer channels Jennifer C. Case, Nicholas A. Pohlman Helical wire coil inserts are used to enhance heat transfer in high heat flux cooling channels. Past research using temperature probes has sufficiently proven that wire coils increase heat transfer by factors of three to five through the disruption of the boundary layer in the channels. The coils are passive devices that are inexpensive to manufacture and easily integrate into existing heat exchangers given the limited pressure drop they produce. Most of the fluid mechanics research in flow over helical coils has focused on the dynamics and vortex structure in fully developed regions rather than the short transition region where the enhanced heat transfer is often expected. Understanding how the development of the flow occurs over the axial length of the cooling channel will determine minimum dimensions necessary for enhanced heat transfer. Results of particleshadow velocimetry (PSV) measurements report on the flow velocities and turbulence that occurs in the transition regions at the beginning of wire coil inserts. The ability to relate parameters such as flow rate, wire diameter, coil pitch, and the total tube length will increase fundamental knowledge and will allow for more efficient heat exchanger designs. [Preview Abstract] 

F1.00106: Characterization of shear turbulence in Keplerian systems Zoe Yan The process by which astrophysical Keplerian disks transport angular momentum is not well understood. Cool protoplanetary disks may not be sufficiently ionized for magnetohydrodynamic forces to assist accretion and prompts the question of whether a hydrodynamic pathway for angular momentum transport is possible. The Hydrodynamic Turbulence Experiment studies turbulence evolution in differentially rotating systems. Ekman effects are mitigated by controlling the axial boundary conditions with rings which rotate independently of the inner and outer cylinders. Azimuthal and radial velocities are measured locally using a Laser Doppler Velocimetry diagnostic. Turbulence decay timescales and Reynolds stress were inferred from these measurements. The interaction of turbulence and rotation is probed by forcing perturbations from a set of configurable jets mounted on the inner cylinder. In all cases examined, the turbulence dies away exponentially, suggesting that at least for the perturbation amplitudes achieved, no subcritical transition exists in these systems. Lifetimes of turbulent states will be presented as a function of the dimensionless shear. [Preview Abstract] 

F1.00107: On SelfSimilarity of Turbulent Flows over Porous Media Ariane Papke, Ilenia Battiato Coupled flows through and over porous layers occur in a variety of natural phenomena, biological systems and industrial processes. Some examples include turbulent flows over sediment beds, urban canopies, polymer brushes and packedbed heat exchangers. Though such systems span a broad range of spatial scales, recent experiments [Ghisalberti, 2009] suggest the existence of a selfsimilar behavior. In this work we employ a twodomain approach to model flow through and over a porous medium: it couples the Reynolds with the DarcyBrinkman equation, and allows one to derive analytical expressions of relevant quantities, such as interfacial velocity and drag length scale, just to mention a few. The connection between our analytical results and experimental data is discussed. [Preview Abstract] 

F1.00108: ENERGY 

F1.00109: Dynamic behavior of lowdimensional model for double diffusive natural convection Yohsuke Yamada, Riyota Takeuchi, Hiroshi Gotoda From the viewpoint of a nonlinear dynamical system, an understanding of the physics in the double diffusive natural convection is crucial in presentday engineering and natural science. We discuss the dynamic behavior of the intermittent chaos region in the double diffusive natural convection produced by a fifthorder nonlinear dynamical system. After the intermittent chaos region become complex with increasing normalized Rayleigh number, it undergoes a significant transition to steadystate through reverse perioddoubling bifurcation cascade. The dynamic properties of the phase space are investigated in detail in this presentation, which have not been reported in previous theoretical research on dynamical systems. [Preview Abstract] 

F1.00110: Numerical study on heat transfer and flow of natural convection in a square enclosure with two vertically aligned cylinders Yong Gap Park, Man Yeong Ha, Hyun Sik Yoon This study investigates natural convection in a square enclosure with two hot inner cylinders induced by a temperature difference between a cold outer enclosure and two hot inner circular cylinders. The centers of two equidiameter cylinders are placed at those of the lower and upper half of the enclosure, respectively. The immersed boundary method (IBM) to model the inner circular cylinders based on the finite volume method is used to study a twodimensional natural convection for different Rayleigh numbers varying from 10$^{3}$ to 10$^{6}$. The effect of the distance between two inner cylinders in an enclosure on heat transfer and fluid flow at different Rayleigh numbers has been examined. The distance between two inner cylinders is changed from 0.1 to 0.5. The natural convection bifurcates from steady to unsteady depending on Ra and the distance between two inner cylinders . The flow and thermal fields eventually reach steady state regardless of the distance between two inner cylinders in the range of Rayleigh numbers from 10$^{3}$ to 10$^{5}$. However, for Ra = 10$^{6}$, there exist unsteady regions depend on the distance between two inner cylinders. [Preview Abstract] 

F1.00111: A numerical study of natural convection in a square enclosure with a circular cylinder at different temperature of bottom surface Minsung Kim, Man Yeong Ha, Hyun Sik Yoon The physical model considered here is a square enclosure of fluid heated below and cold above with a hot cylinder placed at the center of the square. The bottom of square enclosure has dimensionless thermal isothermals of 0 to 1.0. The immersed boundary method (IBM) to model an inner circular cylinder based on finite volume method (FVM) is used to study for different Rayleigh numbers varying over the range of 10$^{3}\sim $10$^{6}$. The dimensionless temperature of the bottom wall is changed along the hot cylinder located the center of the square. This study investigates the effects of the temperature of bottom wall and the buoyancyinduced convection on heat transfer and fluid flow. Detailed analysis results for the distribution of streamlines, isotherms and Nusselt number are presented in this paper. [Preview Abstract] 

F1.00112: Prediction of thermal hydraulic characteristics inside the storage tank of a horizontal condensation heat exchanger using MARSKS Byung Soo Shin, Kwang Won Seul, Kyu Sik Do The performance of a horizontal condensation heat exchanger is determined by the condensation heat transfer inside the heat exchanger tubes, convective or boiling heat transfer outside the tubes and flow characteristics in the storage tank. The flow characteristics in the tank are important factors to determine the heat transfer rate outside the tubes. The objective of this work is to develop the method to predict the heat transfer rate outside the tubes properly using MARSKS code. Two different results from MARSKS were compared with simplified experimental results in other works to estimate the capacity of MARSKS. One was by a typical 1D nodalization but another was by a 3D nodalization considering natural circulation in the storage tank. Then, to eliminate the effect of condensation heat transfer inside the tubes, the experimental results on temperature profiles were applied to the inside wall of tubes as boundary conditions. As the result, the 3D nodalization model had good predictions with experimental results in regard of wall temperature, heat flux and heat transfer coefficients. It was also confirmed that the natural circulation flow was developed inside the storage tank. [Preview Abstract] 

F1.00113: Heat transfer and fluid flow of solidliquid twophase media of different heat conductivities Takaaki Tsutsumi, Shintaro Takeuchi, Takeo Kajishima A direct numerical simulation of particleladen flows, which incorporates the effects of temperature gradient within solid object and heat conduction through moving boundaries, is applied to investigate the heat transfer in a dispersed twophase media. The momentum exchange at the fluidsolid boundaries is treated by our immersed solid approach. A fluxdecomposition scheme is proposed for the heat conduction at the interface. Then we developed an implicit scheme which has wide ranges of applicability for solidfluid density and heatconductivity ratios, Reynolds number and Rayleigh number. A twodimensional natural convection of a mixture composed by liquid and dispersed circular particles of neutral density, confined in a square domain, is simulated. Influences of heatconductivity ratio and volumetric fraction of solid in the liquid are particularly observed. In case of relatively low volume fraction of solid, the scale of circulating flows is dominated by the heatconductivity ratio. In case of dense concentration of particles, the heat transfer due to interparticle connections and/or vibratory motions of particles become pronounced. Overall, these findings highlight the importance of temperature distributions within the particles as well as in the liquid. [Preview Abstract] 

F1.00114: Modeling thermophoretic deposition of particles from a hot fluid stream Zachary Mills, Wenbin Mao, Alok Warey, Anil Singh Bika, Venkatesh Gopalakrishnan, Alexander Alexeev We developed a three dimensional computational model to examine the deposition of aerosol particles in heat exchangers. Our model combines a thermal lattice Boltzmann model for simulating the fluid flow and temperature distribution in the heat exchanger and a Brownian dynamics model that is used to model the transport and deposition of aerosol particles. In our simulations, we investigated particle deposition resulting from convection, thermophoresis, and diffusion. To validate our model we directly compare the simulation results with experimental data for the deposition of particles in a model heat exchanger. We augment our model with a model that describes particle adhesion to the heat exchanger walls. It allows us to examine the formation and buildup of the deposit layer for different flow conditions and particle distributions. Thus, our results provide useful insights into the deposit formation process that are needed for designing heat exchangers that a less prone to fouling. [Preview Abstract] 

F1.00115: Geometric Effects on Power Generation by Reverse Electrodialysiswith Selfinduced Electrolyte Flow in IonSelective Nanochannels Byoung Jae Kim, DongKwon Kim, SeungHyun Lee Recently, solidstate nanofluidic channels or nanopores have been demonstrated experimentally to serve as ionselective membranes for small reverse electrodialysis systems. Ions of opposite charge to that of the surface (counterions) are attracted toward the surface while ions of like charge (coions) are repelled from the surface. As a result, the counterions are preferentially transported over the coions in the charged nanochannels. Under a concentration gradient, the ions diffuse spontaneously across the nanochannels, and a portion of the Gibbs free energy of mixing can be harvested continuously from the nanochannels by means of the net diffusion current. In the present study, power generation by reverse eletrodialysis in ionselective nanochannels is numerically investigated by solving the NernstPlanck equation for the ionic concentrations, the Poisson equation for the electric potential, and the NavierStokes equation for the electrolyte velocity simultaneously. We elucidated the effect of various parameters on power generation such as geometry of channel cross section, channel length, hydraulic diameter and the surface charge density etc. [Preview Abstract] 

F1.00116: An experimental investigation into the effect of Marine Hydrokinetic (MHK) turbine array spacing on turbine efficiency and turbine wake characteristics Nick Stelzenmuller, Alberto Aliseda Three 1/45 MHK turbine scale models were tested in a flume at various array spacings. The model turbines were instrumented to measure torque and angular velocity. Incident flow on the turbines and in the wakes was characterized via PIV and ADV measurements. Flow characteristics: mean velocity, turbulence intensity, and vorticity are correlated with turbine performance. Tip speed ratio (TSR) similarity (although not Reynolds number) of the turbines is achieved by controlling the applied load with magnetic brakes inside the model turbine nacelles. Wake characteristics and turbine efficiencies were investigated at a range of TSRs, with the goal of ``tuning'' an array to maximize overall array efficiency. Grids were placed in the flume upstream of the turbine array in order to change the turbulence intensity of the flow incident to the array. High levels of turbulence intensity in the incident flow is consistent with natural conditions in tidal currents, and has a strong effect on turbine wake dissipation. These experiments used a ``reference model'' turbine geometry developed for DOE at the National Renewable Energy Laboratory for the purpose of facilitating the comparison of experimental and numerical results in marine hydrokinetic turbine research. [Preview Abstract] 

F1.00117: Windblown dust emission, transport and deposition in solar farms Chuanjin Lan, Zhen Li, Yanbao Ma Dust accumulation on solar collectors can significantly reduce the electrical output of solar farms. The presence of solar panel array can significantly accelerate or decelerate wind speed and distort the wind velocity profiles near the ground, which leads to considerable changes in dust emissions, transportation as well as deposition. To examine the effects of solar panels on dust emission, transportation and deposition, the incompressible viscous flow past flat solar panels with ground effect was numerically investigated based on finite volume method. A hybrid approach known as detachededdy simulation (DES), combining the main features of both largeeddy simulation (LES) and Reynoldsaveraged NavierStokes (RANS), is utilized to the compute the turbulence flow. Results show how aerolian dust emissions, transport and deposition are affected by wind speeds, solar panel orientation angles and panel geometries. [Preview Abstract] 

F1.00118: Detachededdy simulations of hydrokinetic turbines using actuator disks Domenico Sciolla, Cristian Escauriaza The development of new technologies to harness energy from tidal currents in coastal areas requires an understanding of the interaction of the flow over arbitrary bathymetries and the marine hydrokinetic (MHK) turbines that can be potentially installed at a specific site. When computing realistic flows past multiple MHK devices, numerical models should satisfy the following attributes: (1) Resolve the rich dynamics of the wakes to capture the instantaneous interactions of the turbulent coherent structures; (2) Deal with complex arbitrary bathymetries of the natural channels; and (3) Employ lowcost modeling techniques to incorporate the regions of interest with good resolution and multiple turbine arrangements. In this investigation we simulate the flow past porous disks using the detachededdy simulation approach (DES). The results show that the model reproduces accurately the mean flow and turbulence statistics of the wakes, and constitutes a powerful tool for analyzing the flow field in realistic conditions using low computational resources. The simulation results are also employed to determine the forces induced by the turbine array on the entire flow, parameterizing its effects to be incorporated in regionalscale models. [Preview Abstract] 

F1.00119: Analysis of Tumble and Its Effects on EGR Tolerance for a Gasoline Engine Running at High Loads Jordan Easter, Paulius Puzinauskas, Timothy Pyles The series hybrid electric vehicle allows for the design of an engine that can run solely at its most efficient point, wide open throttle (WOT). However, at WOT there is an increase in emissions not typically handled in the conventional gasoline engine. Exhaust gas recirculation can be used to reduce emissions if the tolerance of the engine for the exhaust gas is increased. It is hypothesized that tolerance at WOT will increase when there is an increase in incylinder turbulence. In this research, aluminum flow guide vanes were inserted in the intake to induce tumble. The flow was examined through the use of PIV techniques and the increase in EGR tolerance was verified with engine testing. PIV images of the flow structure were taken between the intake valves of a modified cylinder designed to mimic bottom dead center. The lift to valve diameters as well as the vane configurations were altered. Engine testing was performed with varying vane configurations, while the EGR percentage was increased until it became difficult to control combustion. It was been found through the engine testing that the flow guide vanes do significantly increase the EGR tolerance as well as combustion stability. [Preview Abstract] 

F1.00120: InDepth Absorption of Thermal Radiation in Phase Change Materials Laura Pershern, Morgan Minton, John Baker Performance of a direct absorption solar thermal collector employing a phase change material (PCM) will be directly impacted by the radiant properties of the PCM. Melting and solidification behavior of paraffin, a commonly used PCM, exposed to an external thermal radiation field was investigated. As radiant properties of paraffin are different with respect to solid and liquid phases, the absorption of thermal radiation within the paraffin will be different in the two phases. It is hypothesized that this fact will change the melting and solidification behavior of the paraffin. The solidliquid interfacial position was recorded as a function of time for heating from above for varying incident radiant intensities. When observed, flow structure was recorded. A onedimensional heat transfer model was used to gain insight into the temperature behavior with the solid phase. [Preview Abstract] 

F1.00121: Flow through porous media with fractal geometry: effect of wettabilty D. Hernandez, O. Chavez, R. Zenit We experimentally analyze the behavior of twophase flow through porous media with a fractal geometry. We are interested in this particular case because it has been shown that many oil wells posses a fractaltype porosity structure. In the laboratory, fractal porous media were prepared considering arrays of glass spheres of different diameters and volumetric proportions. To vary the wettability, which is another factor of great importance for oil extraction, the glass spheres was treated with a hydrophobic coating. By measuring the pressure drop and the flow rate, the relative permeability was determined. Additional, some flow visualization experiments were conducted. We found that the relative permeability increases as the wettability decreases: air bubbles tend to remain in contact with the glass surfaces, while the fluid tends avoid them. We also discuss the changes of permeability for fractal and nonfractal porous media. [Preview Abstract] 

F1.00122: GEOPHYSICAL 

F1.00123: Simulation based study of the effect of ocean waves on floating wind farm Di Yang, Charles Meneveau, Lian Shen A hybrid numerical capability is developed for the simulation of floating wind farm offshore, in which largeeddy simulation is performed for wind turbulence, and a potential flow based method is used for the simulation of ocean wavefield. The wind and wave simulations are coupled through a twoway feedback scheme. The effect of wind turbines on the wind field is represented by an actuator disk model. A variety of fullydeveloped and fetchlimited windsea conditions are considered in the study. The simulation results indicate that the offshore wind farm obtains a higher wind power extraction rate under the fullydeveloped windsea condition compared with the fetchlimited condition. This higher extraction rate is caused by the faster propagating waves and the lower seasurface resistance on the wind when the windseas are fully developed. Such wave effect becomes more prominent when the turbine density of the wind farm increases. [Preview Abstract] 

F1.00124: Internal waves and turbulence created by tidal flow over smallscale topographic features Masoud Jalali Bidgoli, Narsimha Rapaka, Sutanu Sarkar Numerical simulations are used to study the internal waves and turbulence generated by the oscillation of a barotropic tide over bumps of small length scale where the tidal excursion number, $Ex$, i.e., the ratio of tidal excursion length to the topographic width is order unity. The objective is to go beyond linear theory to assess the effect of tidal excursion number. Subcritical to supercritical slope angles are considered to investigate if slope angle in conjunction with excursion number leads to different regimes. At low values of $Ex$, the results agree with Rapaka et al (2011) but there are significant differences in the $Ex = O(1)$ limit. The internal wave field is characterized using spectra, modal analysis and the baroclinic energy budget. Qualitative differences in turbulence generation, phasing and energetics are found when $Ex$ increases. [Preview Abstract] 

F1.00125: Effect of the bottom profile on coastal topographic waves Gerardo Ram\'Irez Rosario, Luis Zavala Sans\'on We consider linear shallow water equations (LSWE), for a straight coast whose profile is given by $H(x)=\alpha x^{s}$, where $s$ is a positive real number and $x$ is the distance perpendicular to the coast. We show how the LSWE can be transformed in to an ordinary differential equation, which is solved by perturbation methods. The perturbation term depends on wave frequency, the Coriolis parameter and geometric features of the coast and decays exponentially with offshore distance. The solutions of the unperturbed problem are the associated Laguerre polynomials. These polynomials are the basis for finding approximate solutions of the perturbed problem. For the case $s=1$ the method recovers the solution reported in the literature. The dispersion relation of the unperturbed problem corresponds to that obtained with the rigid lid approximation. The dispersion relation shows that for small $s$ subinertial modes are less affected by topography than superinertial modes. However, for large $s$ subinertial modes are more affected than superinertial. An interesting case is $s=2$, since the eigen frequencies do not depend on wave number. [Preview Abstract] 

F1.00126: Numerical experiments of atmospheric flow off Baja California, M\'{e}xico Carlos Torres, Sergio Larios, Adan Mejia, Jaime Garcia, Eduardo Gil In order to simulate flow structures suggested by satellite images of cloud trails off Baja California, the momentum primitive equations describing an atmospheric flow over that region are solved numerically on a boundaryfitted grid. Numerical experiments are conducted for several flow conditions. Results show a remarkable agreement to available observations. [Preview Abstract] 

F1.00127: Thermally Driven Flow in a Mock Street Canyon Ann Dallman, Sigurdur Magnusson, Leslie Norford, Harindra J.S. Fernando, Dara Entekhabi, Rex Britter, Shanshan Pan Under conditions of low synoptic winds and high solar radiation, nonuniform heating of building walls and the ground in an urban street canyon induces thermallydriven airflow. These effects have mainly been studied using windtunnel experiments and numerical models, but only a few fieldscale experiments have been performed. However, this is an important topic of interest because of its implications for air quality and emergency response planning. A field experiment was carried out in collaboration between the SingaporeMIT Alliance for Research and Technology (SMART) and the University of Notre Dame. The study was conducted on the campus of Nanyang Technical University in Singapore, and consisted of an `idealized' building canyon constructed with two rows of shipping containers aligned in the NorthSouth direction. The site was carefully instrumented with sonic anemometers (for wind speed and direction and virtual temperature), weather stations (wind speed and direction, temperature, relative humidity, pressure, and rain fall), and thermocouples (surface temperature of buildings). Measurements were recorded for 9 days, which included periods of sunshine and high convective activity that created thermal circulation between the buildings. Using a fog machine, flow visualization was carried out to observe circulation patterns. An overview of the experiment and the results will be presented. [Preview Abstract] 

F1.00128: Ventilation Exhaust Power Recovery Design Jeremy Yandell, Alberto Aliseda Due to the expense of designing ductwork and exhaust fans to meet the exact desired flow rate for building exhaust, there is wasted energy that is unrecovered when exhausted to the atmosphere. By designing a small diameter wind turbine the kinetic energy in the exhaust stream can be recovered and power provided back into the building. Unlike large scale commercial wind turbines that must be designed to provide power from a large range of wind speeds and directions, this smaller scale turbine can be optimized for a single constant wind speed with no variation in direction. The critical component is to prevent backpressure feeding through the system and increasing the load on the exhaust fan. This design project began with the theoretical airfoil and blade design, followed by modeling the system in fluid dynamics software, a full CAD design was created and modified for the selected manufacturing process, prototype creation and testing will be completed both in a wind tunnel and in a real environment, and the completed data will be compared with theoretical and computational results. Note: There is a patent pending for this design and concept. [Preview Abstract] 

F1.00129: Computational Analysis of Flow Field Hydrodynamics Between Identical Spheres in Water Gaurang Shyam Limachia Stokes' Law is the foundation of modern hydrodynamics. The introduction of rigid particles into a uniform flow makes the governing equations highly complex; consequently, these equations are nearly impossible to resolve analytically. As a result, solutions are often found for specific instances through numerical analysis. This paper performs such numerical analysis for rigid spheres suspended in a single fluid with uniform upward flow. The perturbation of the velocity field was found to be greatest when the spheres were within 1.30 Diameters of each other. In contrast, the spheres moved independently with minimum interaction at distances greater than 5 Diameters apart. This research helps us identify ideal interaction distances for suspended objects and understand the natural orientation of real organisms traveling in real fluids in the real world. [Preview Abstract] 
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