Bulletin of the American Physical Society
61st Annual Meeting of the APS Division of Fluid Dynamics
Volume 53, Number 15
Sunday–Tuesday, November 23–25, 2008; San Antonio, Texas
Session LZ: Poster Session (15:15 - 17:00) |
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Room: Ballroom A |
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LZ.00001: Design, construction and characterization of a solar thermoacoustic engine Fabrisio L. G\'omez, Guadalupe Huelsz We designed, constructed and characterized a thermoacoustic engine that operates with solar radiation concentrated by a Fresnel's lens. The resonator is a Pyrex tube closed in one of its ends and opened in the other one. The stack is built of a ceramic piece with parallel channels. The Fresnel's lens concentrates the direct solar radiation on the end of the stack near to the closed end of the resonator. A structure supports the elements of the engine and allows following the direct solar radiation in a manual form. The acoustic pressure amplitude of the generated stationary wave was measured with a microphone located 1 cm away from the opened end, but it was impossible to measure it in the closed end since the concentrated solar radiation goes through this end, and the placement of any microphone would obstruct its passage. Therefore we made an engine warmed by an electrical resistance in which it is possible to place a microphone in both ends of the resonator. Using the electric engine we reproduced the wave generated by the solar engine to estimate the acoustic pressure amplitude in its closed end. [Preview Abstract] |
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LZ.00002: Helical structure of longitudinal vortices embedded in turbulent wall-bounded flow Clara Velte, Martin Hansen, Valery Okulov Embedded vortices in wall-bounded flow over a flat plate, generated by a passive rectangular vane-type vortex generator with variable device angle $\beta$ to the incoming flow in a low- Reynolds number flow ($U_{\infty} = 1.0\, ms^{-1}$), have been studied using Stereoscopic PIV in the respect of helical symmetry. The vortices possess helical symmetry, allowing the flow to be described in a simple fashion. A model describing the flow has been utilized, showing strong concurrence with the measurements. Through the swirl parameter it was possible to predict the helical pitch. The pitch, vortex core size, circulation and the advection velocity of the vortex all vary linearly with $\beta$. One can thereby determine the axial velocity induced by the helical vortex as well as the swirl for a given $\beta$. This also simplifies theoretical studies, e.g. to understand and predict the stability of the vortex and to model the flow numerically. [Preview Abstract] |
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LZ.00003: Minimum Drag Shape of a Hemi-ellipsoid Exposed to Shear Flow and Its Possible Relation to Deformation of Arterial Endothelial Cell Dong Wook Lee, In Seok Kang As a model problem for an endothelial cell subject to blood flow, we consider a hemi-ellipsoid attached to a wall in the imposed shear flow. The minimum drag shape is obtained under the condition that the volume is kept constant. The aspect ratio of major axis to minor axis of the minimum drag shape turns out to be close to those of the equilibrium shapes of endothelial cells under steady blood flow. This fact suggests that there might be a possible connection between the objective function of drag minimization and the feedback mechanism for shape adjustment of an endothelial cell. From the fluid mechanics point of view, this mechanism can be considered as that the endothelial cell adjusts its shape in a way to minimize the drag force exerted by the shear flow. The analytical solution to the model problem is not available. So, the problem is solved numerically to compute the drag force exerted on the hemi-ellipsoid. However, an analytical solution is available for a closely related problem, which is the problem of a fixed ellipsoid in a shear flow. When the upper half domain is considered, the analytical solution satisfies everything of the original problem except for the velocity y-component at the flat surface. The analytical solution is Jeffery's classic result on the motion of an ellipsoidal particle in a viscous fluid [Proc. Roy. Soc. A (1922)]. [Preview Abstract] |
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LZ.00004: The influences of curvature and torsions on flows in a helical bifurcated stent-graft Jeong Hyun Shim, Kyung Eun Lee, Jung Yul Yoo A bifurcated stent-graft signifies an improvement in surgical technique for treatment of a lesion in the branched blood vessel. However, there still remains a high failure rate regarding bifurcated stent-graft due to the occurrence of thrombosis or re-stenosis. The objectives of this study are to understand the effect of torsion in helical bifurcated geometries, to explain how the mixing of flows there may be advantageous to the prevention of the occurrence of thrombosis, and to keep the patency of stent-graft in the aspect of hemodynamics. For clinical applications, flows in a helical bifurcated stent-graft are simulated three-dimensionally using an incompressible Navier-Stokes solver. In this study, the hemodynamics is investigated in terms of mechanical factors, i.e., velocity profiles, vortex patterns and wall shear stress distributions. [Preview Abstract] |
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LZ.00005: Migration of connexin in the membranes of living cells Matthew Bledsoe, Daharsh Rana, Karl May, Jennifer Kreft Movement of connexins within cell lipid bilayers remains somewhat mysterious. In studying their movement, researchers hoped to shed more light on the mechanisms by which they are influenced. We examined this problem by observing the behavior of the connexins directly. Cancerous human liver cells were cultured and their membrane connexins labeled with green fluorescent protein through transvection. The connexins were then filmed by high speed camera and carefully analyzed. The study served to fine-tune the model used in simulations of connexin migration, enabling further study of connexins and their transmembrane environment. [Preview Abstract] |
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LZ.00006: Nonlinear effects in the dynamics of viscous vesicles in linear flows Petia M. Vlahovska, Yuan-Nan Young Vesicles in a simple shear flow deform into prolate ellipsoids and exhibit at least three (experimentally confirmed) types of behavior: tank-treading (also observed for drops), tumbling and breathing (new features that are unique for vesicles). This non- trivial dynamics originates from the distinctive mechanical properties of the lipid bilayer membrane: the molecularly thin membrane is a highly-flexible incompressible fluid sheet. Several groups have studied vesicle behavior in steady shear flow. The phase diagram suggests that when subjected to linear flow with some variable parameter, vesicle transition between different states can show hysteresis. We examine dynamics of vesicles subjected to time-varying flows: oscillatory shear and linear flows with variable rotational component. Floquet analysis is conducted to investigate the vesicle dynamics and conditions for chaotic shape and flow dynamics are established. [Preview Abstract] |
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LZ.00007: Taylor-Couette Flow with Hourglass Geometry of Varying Lengths Simulated by Reaction-Diffusion Yunjie Zhao, Andrew Halmstad, Thomas Olsen, Richard Wiener Previously, we have observed chaotic formation of Taylor-Vortex pairs in Modified Taylor- Couette Flow with Hourglass Geometry.\footnote{Richard J. Wiener \textit{et al}, Phys. Rev. E \textbf{55}, 5489 (1997).} In the experiment, the chaotic formation in a shorter system has been restricted to a narrow band about the waist of the hourglass. Such behavior has been modeled by The Reaction-Diffusion equation,\footnote{H. Riecke and H.-G. Paap, Europhys. Lett. \textbf{14}, 1235 (1991).} which has been previously studied, by Riecke and Paap. Their calculation suggested that quadrupling length of the system would lead to spatial chaos in the vortex formation. We present a careful recreation of this result and consider an intermediate length. We demonstrate that doubling the length should be sufficient to observe spatially chaotic behavior. [Preview Abstract] |
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LZ.00008: Control of the Damped, Driven Pendulum, in both Numerical Models and Physical Apparatus to develop algorithms appropriate to the control chaotic formation of Taylor Vortex Pairs in Modified Taylor-Couette Flow Eric Douglass, Yunjie Zhao, Lucas Hill, David Brenman, Thomas Olsen, Richard Wiener Chaos has been observed in the formation of Taylor Vortex pairs in Modified Taylor Couette flow with hourglass geometry.\footnote{Wiener \textit{et al}, Phys. Rev. E \textbf{55}, 5489 (1997).} Control of chaos has been demonstrated in this system employing the RPF algorithm.\footnote{Rollins \textit{et al}, Phys. Rev. E \textbf{47}, R780 (1993).}$^,$\footnote{Wiener \textit{et al}, Phys. Rev. Lett. \textbf{83}, 2340 (1999).} Seeking alternative algorithms, we are implementing the OGY\footnote{E. Ott, C. Grebogi, \& J. A. Yorke, Phys. Rev. Lett. \textbf{64}, 1196 (1990).} algorithm in a numerical model\footnote{G. L. Baker, Am. J. Phys. \textbf{63}, 832 (1995).} of a damped driven mechanical pendulum and a physical apparatus.\footnote{J. A. Blackburn \textit{et al}, Rev. Sci. Instr. \textbf{60}, 422 (1989).} We report on both and future plans for the Modified Taylor-Couette system. [Preview Abstract] |
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LZ.00009: Theoretical Studies of Transport within Single Walled Carbon Nanotubes Paul Maldonado, Hernan Martinez Carbon nanotubes have exciting electrical and mechanical properties that seem attractive for ionic and non-ionic transport. However, some fundamental questions about this transport are still not completely understood. One of these questions is how the ion transported through the nanotube is affected by the force and electric fields of the nanotube due to its size and charge. For this investigation to be done, a theoretical structure for a (5,5) single walled carbon nanotube (SWCN) is created by optimizing the geometry of a (5,5) SWCN using semi-empirical PM3 methods. With that optimized structure, computer simulations are performed based on Molecular and Brownian Dynamics techniques to analyze the diffusion through the SWCN. We calculate diffusion coefficients, mean square displacement as well as concentration profiles for both ionic and non-ionic particles moving through them. [Preview Abstract] |
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LZ.00010: Migration of Connexin in the Membranes of Living Cells: Computational Method Karl May, Daharsh Rana, Matthew Bledsoe, Audrey Hammack, Jennifer Kreft The membranes of living cells are semi-permeable layers that contain phospholipids and numerous proteins. Connexin, specifically, is a gap-junction protein found in the membrane that is imperative in the communication between cells. We utilized a lattice Boltzmann simulation to model the motion of connexin within a cellular membrane. The phospholipids are considered a uniform fluid in the simulation. The model membrane contains solid obstacles that impede the movement of connexin, thus causing the protein to become trapped in domains for various periods of time. The results from the computational model have been used to quantitatively match the results of an experiment involving cells with connexin labeled by green fluorescence protein. We also use the simulation to investigate different mechanisms by which connexin migrates to the point of contact between cells. [Preview Abstract] |
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LZ.00011: Heat Convection in a Vertical Channel Jean-Christophe Tisserand, Mathieu Creyssels, Mathieu Gibert, Bernard Castaing, Francesca Chill\`a The Rayleigh-Benard flow, heat convection between two horizontal plates at different temperatures, has been the most studied system of thermal convection. Recent controversies stressed the interest of a better knowledge of the bulk flow. However,~ in this situation, the heat transfer is mainly controlled by the neighborhood of the plates. Therefore, we had to build a vertical long channel in which the flow forgets the plates. In this configuration, the flow is, either globally ascending in the left part, and descending in the right one, or the opposite. The paper focuses in a first part on the study of these flow-reversals thanks to correlation functions and particle image velocimetry. In a second part, the paper gives an interpretation of results in terms of velocity of plumes. [Preview Abstract] |
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LZ.00012: Laboratory measurements of energy and temperature dissipation rates in Rayleigh-Bernard convective flow with Ra= O(10$^8$) to O(10$^9$) Sarah Woods, Adam Fincham, Darek Bogucki The measurements were carried out in a Rayleigh-Bernard convective cell with dimensions 0.3 m x 0.3 m x 0.3 m. We have experimentally obtained time series of temperature collocated with velocity fields from a 2D PIV system.~The length of the time series spans a few large eddy turnover times, allowing the capture of energy and temperature fluctuations. We have used PIV interrogation windows smaller than the Kolmogorov scale, permitting calculation of the energy dissipation rates.~The energy dissipation rates were calculated using methodology following (Fincham et al. 1996). The temperature variance dissipation rates were calculated using collocated time series of microscale velocity and temperature fluctuations. The obtained temperature variance dissipation rates were compared to the measurements of this quantity performed using optical techniques following (Bogucki et al. 2007). The structure of the large scale velocity flow reflects the observations of (Xia et al. 2003), while we note some departure of the PDF of temperature and velocity from a Gaussian distribution. [Preview Abstract] |
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LZ.00013: Bifurcations in convection of incompressible fluid in a rotated square cylinder Albert Sharifulin, Sergey Suslov The 2D convection of air in a long horizontal square cylinder two opposite side walls of which are thermally insulated and the other two are maintained at constant but different temperatures has been considered. The cavity is gradually rotated about its horizontal axis. It is found that a multitude of stationary bifurcating solution exist depending on the inclination angle and the Rayleigh number. Normally and abnormally rotating solutions are defined and distinguished and the bifurcation curve is computed. [Preview Abstract] |
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LZ.00014: Capillary forces during liquid nanodispensing Thierry Ondarcuhu, Hugo Durou, Aiping Fang Liquid nanodispensing (NADIS) is a recently developed method to deposit and manipulate small volumes of liquids (down to 100 zeptoliter) on a surface [1]. This atomic force microscope (AFM)-based method uses a nanochannel milled by focused ion beam (FIB) at the apex of a hollow AFM tip to transfer liquid from a reservoir located on the cantilever, to the surface. The smallest droplets (70 nm in diameter) contain, for standard dilutions, only few molecules opening the way to single molecule deposition. We present here a study of the capillary force exerted on the tip during the deposition. Using the ``surface evolver'' software, we simulated the force curves measured by AFM, which is the only available data during deposition. The good agreement between experimental and calculated curves gives important information on the liquid transfer mechanism and provides a real-time control of the deposition during the process [2]. \\[0pt] [1] A.Fang, E. Dujardin, T.Ondarcuhu, NanoLett. 6 (2006) 2368. \\[0pt] [2] T.Ondarcuhu et al, Eur. Phys. J. ST. (2008) in press. [Preview Abstract] |
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LZ.00015: Nonlinear hydrodynamic phenomena in Stokes flow Jerzy Blawzdziewicz, Eligiusz Wajnryb, Yuan-Nan Young The inertial term in the Navier--Stokes equations gives rise to numerous nonlinear phenomena, such as flow instabilities, formation of complex convective patterns, and turbulence. In our presentation we will discuss nonlinear behavior of a fluid under Stokes flow conditions, i.e., with no inertial forces. The fluid-dynamics equations are thus linear---the nonlinearity of the system stems entirely from the boundary conditions. We will consider (a) the dynamics of a highly viscous drop in 2D linear flows with rotation and (b) the motion of regular particle arrays in Poiseuille flow in a parallel-wall channel. We show that the drop response to quasistatic vorticity change is hysteretic, and at higher frequencies of the external forcing, the system undergoes a cascade of period-doubling bifurcations leading to chaos. We also demonstrate that the evolution of regular particle arrays in parallel-wall channels leads to emergence of complex patters that include separation of double rows of particles from the main body of the array, coexistence of ordered and disordered regions, rearrangements of regular particle lattice along dislocation lines, and fingering instabilities. [Preview Abstract] |
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LZ.00016: Evolution of precursor film in front of the moving contact line of spreading drop Anna Hoang, Pirouz Kavehpour For wetting fluids, a microscopic film, which is known as the precursor film, exists at the front of the moving contact line. The structure of this thin film has been studied theoretically, but previous experimental investigations were limited by the resolution of the measurement system (lateral or vertical) required to capture the complete scope of this feature. We studied the evolution of the profile of a spreading droplet near the moving contact line using a total internal reflection fluorescence microscope (TIR-FM). The features of the macroscopic drop (spherical cap), wedge region, and precursor film were investigated within a single experiment. This was made possible by the lateral resolution and dynamic range of our technique. The dynamic characteristics of the precursor films have a good agreement with the available theoretical results. [Preview Abstract] |
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LZ.00017: Growth and shape of bubbles in viscous liquids and confined geometries Arnulfo Ortiz, Abel Lopez, Francisco Higuera, Abraham Medina In this work we have considered the problem of the growth and detachment of bubbles in a viscous liquid in finite reservoirs where axisymmetrical walls were located near the gas injection orifice. We studied numerically and experimentally how the coaxial pipe and inverted-cone walls affect the shape, final volume and coalescence of bubbles under conditions of constant gas flow rate, Q. The numerical solution of the Stokes equations and the free surface were determined as a function of a capillary number and Bond number in the absence of inertial effects. Detailed experimental visualizations are presented that display the sequences of growth and detachment computed numerically. [Preview Abstract] |
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LZ.00018: Field-induced motion of ferrofluid droplets through immiscible viscous media S. Afkhami, Y. Renardy, M. Renardy, J. Riffle, T. St Pierre The motion of a hydrophobic ferrofluid droplet placed in a viscous medium and driven by an externally applied magnetic field is investigated numerically in an axisymmetric geometry. Initially, the drop is spherical and placed at a distance away from the magnet. A numerical algorithm is derived to model the interface between a magnetized fluid and a non-magnetic fluid via a volume-of-fluid framework. Results for a range of magnetic Laplace number and magnetic Bond number are given. The time taken by a droplet to travel through a viscous medium and the deformations in the drop are investigated and compared with experimental studies. [Preview Abstract] |
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LZ.00019: Interaction of a contact line with nanometric steps Thierry Ondarcuhu, Agnes Piednoir In order to study the interaction of a contact line with nanometric steps, we investigated the dewetting of polystyrene films on terraced surfaces such as alumina or graphite (T. Ondarcuhu, A. Piednoir NanoLett 5 (2005) 1744-1750). We observed that, for steps heights larger than a critical value, the hole is asymmetric: the contact line is blocked by downwards steps whereas it passes through upwards steps with no interaction. This behavior is explained by simple macroscopic considerations based on the equilibrium contact angle. For steps smaller than this critical value, the contact line is insensitive to the steps: the hole grows symmetrically as on a homogeneous surface. Statistics with various polystyrene over a large number of steps on alumina showed that the critical step height is about 3 times the radius of gyration of the polymer. This indicates that a simple ``macroscopic'' description remains valid down to dimensions of the order of the diameter of one single molecular chain. This result has also important implication for the study of contact angle hysteresis. [Preview Abstract] |
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LZ.00020: The thermogravitational technique at high pressures Pedro Urteaga, Mounir Bou-Ali, Abdelfattah Zebib, Pablo Blanco Thermogravitational columns have been used successfully for over a decade to experimentally determine the thermal diffusion coefficients of binary and ternary mixtures at atmospheric pressure. A homogeneous mixture is placed in a vertical annulus. Species separation occurs due to side heating and thermal diffusion. Combined with buoyancy vertical concentration gradients are induced, measured, and the Soret coefficients deduced. In this work we extend this technique to measurements at the high pressures encountered in oil fields. A detailed description of the high pressure thermogravitational installation is presented. We first validate the new construction by conducting experiments with binary mixtures at atmospheric pressure and comparing our results with those in the literature. Dependence of the thermal diffusion coefficients of various binary mixtures of hydrocarbons and liquids on pressure is given. [Preview Abstract] |
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LZ.00021: Simultaneous Reference- and Pressure-Image Acquisitions for Unsteady Pressure-Sensitive Paint Measurement Kensuke Miyamoto, Takeshi Miyazaki, Hirotaka Sakaue Simultaneous reference- and pressure-image acquisitions using two-color unsteady pressure-sensitive paint (PSP) and a stereo adaptor are presented. Unsteady PSP gives two-color luminescence, which is related to reference- and pressure-images, respectively. Two band-pass filters matching with reference- and pressure-luminescence, respectively, are mounted in front of a stereo adaptor to capture only reference- and pressure-images. The adaptor is connected to a fast frame rate CCD camera that can acquire continuous unsteady pressure field. Our acquisition system has an advantage for unsteady PSP measurements that fluctuate and/or vary reference image in time. The validity of this system is discussed. A demonstration of the present system in unsteady pressure field with model fluctuation is included in the final version. [Preview Abstract] |
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LZ.00022: Experimental spectroscopy for the high-school Physics curriculum Rajeev Kinra, Adonios Karpetis The present work explores the feasibility of including spectroscopic experiments in high-school physics curricula. Two experimental optics ``modules'' were constructed for this purpose: (a) a simple CCD detector, in combination with appropriate filters, was used for the measurement of solar spectra and the determination of the sun's surface temperature; (b) the same detector was used, in combination with a transmissive diffraction grating and some miniature optics, to form a spectrophotometer that can be used for the determination of spectra with high resolution. Both modules were designed and constructed with portability and low cost in mind, and their objective is to introduce experimental spectroscopy to high school students in an intriguing, educational and phase-appropriate manner without sacrificing scientific rigor. A large variety of experiments may be designed around the basic devices that were built during this work, and a number of possible examples will be presented, from research on plant phototropism to human color cognition. [Preview Abstract] |
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LZ.00023: Longitudinal cross sectional mixing images of the pipe flow with periodical branching flow injections Toshihisa Ueda, You Sunho, Naotaka Higuchi Effect of periodical injection of branching flows on the mixing in a pipe flow is experimentally investigated. Glycerin is used as a working fluid. The glycerin flows in a steady state condition in the main flow pipe while the branching flow is injected periodically from three pipes equipped normal to the main flow pipe. The longitudinal cross sectional image of the mixing of main flow and branching flows is visualized by LIF method, inserting the Rodamine B in the first branching flow. When only one branching flow is periodically injected, the fluid injected from the side flow pipe is stretched and folded by the parabolic laminar flow velocity profile and then the length of the boundary increases linearly. When branching flow is injected from multiple side flow pipe, the mixing pattern becomes more complicated. As a result, the length of the boundary increases more rapidly compared to the linear increase. The results suggest that the multiple branching flow injection enhances the mixing although no element is inserted in the pipe. [Preview Abstract] |
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LZ.00024: Streaky 3D Structures in the Boundary Layer Juan Martin, Carlos Martel It has been recently shown [Choi, Nature, April 06 - Cossu, PRL, February 06] that 3D streaky structures in the boundary layer can remain laminar longer than the 2D Blasius flow. The aim of this investigation is to study the possibility of promoting these 3D streaky structures via surface roughness, computing them and evaluating the resulting stabilization using the Reduced Navier Stokes equations (RNS). The RNS are derived from Navier-Stokes making use of the fact that two very different scales are present: one slow (streamwise direction) and two short (spanwise and wall-normal direction). The RNS allows us to perform these 3D computations in a standard PC, without using CPU costly DNS simulations. [Preview Abstract] |
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LZ.00025: Collapsing Mechanism of Toroidal droplets Ekapop Pairam, Alberto Fernandez-Nieves Water drops in oil phase are always spherical in order to minimize interfacial energy. This is why other drop shapes are rarely seen. This report show that we are able to generate millimeter size drops which are topologically different from the sphere, namely a torus. The torus can be made by rotating an outer oil phase fast enough while pumping water through an oil submerging capillary tip. For large values of the capillary number of the outer fluid we can create a circular jet which becomes a full circle to make a torus drop. The fatness of the torus can be control through the volume of infused water and the location of the capillary tip from the center of rotation. The toroidal droplets always evolve into a spherical shape. The mechanism of this process is very interesting. So far we have classified two types of behaviors. For a skinny torii, break-up occurs followed by a slow evolution towards the spherical shape. For fat torii, however, there is no break-up. In this case, the torus gets fatter as a whole ultimately collapsing into a spherical drop. We have quantified the dimensionless growth rate for these two situations and compared our results with predictions based on the Rayleigh-Plateau instability for the experimental viscosity ration; the comparison suggests that more ingredients must be incorporated to explain our data. [Preview Abstract] |
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LZ.00026: Richtmyer-Meshkov Instability in Thin Fluid Layers: Turbulent Mixing, Mach Number and Reshock Effects Gregory Orlicz, B.J. Balakumar, Devesh Ranjan, Christopher Tomkins, Kathy Prestridge A thin air-SF6-air gas curtain is impulsively accelerated by planar shock waves of varying strength (Mach 1.2-1.5) and investigated experimentally using simultaneous concentration field visualization and particle image velocimetry measurements. A novel nozzle design is used to create highly repeatable and flexible initial conditions that allow for isolation of effects on the flow structure due to Mach number and initial modal composition. The effective position of the end wall is also varied to re-shock the evolving structure, accelerating the transition of the flow to a turbulent regime. Turbulence statistics are compared between a single mode varicose curtain, and a multi-mode curtain. These true-ensemble averaged statistics are the first such measurements in variable density turbulent flows in thin fluid layers, and can be used for code validation. [Preview Abstract] |
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LZ.00027: Experimental Investigation of the Stability of a Stratified Fluid Flow Involving a Horizontal Gradient of Density Marshall Newman, Matthew Moore, Rich McLaughlin, Roberto Camassa, Kuai Yu, Keith Grose A vertically moving boundary in stratified fluid can create and maintain a horizontal density gradient, with greater density fluid adjacent to the moving boundary. We have designed an experiment to study the hydrodynamics of this configuration, whereby the moving boundary consists of a fishing line towed vertically through a stably stratified fluid. A shear boundary layer is observed to develop in the fluid resulting in a horizontal density gradient. We measure the size of the shear layer as a function of the speed at which the line is towed. The hydrodynamic instability of this system manifests itself as an apparent jump in this plot. Consequently, we are able to obtain a critical Reynolds number for the stability of this system. We also compare the layer size-to-speed observations with those obtained from an exact mathematical solution which approximates the geometry of the problem in the axial-symmetric case. [Preview Abstract] |
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LZ.00028: Visualization study of the vapor bubble dynamics in the liquid nitrogen flow inside a small tube Peng Zhang, Xin Fu, Ruzhu Wang The vapor bubble nucleation, growing up and detachment in diabatic two-phase flow of liquid nitrogen in a vertically upward tube of 1.33 mm in diameter is experimentally investigated by employing high-speed visualization technique. It can be found from the experiments that the vapor bubble diameter increases linearly with the elapse of the time. The tube wall has the significant effect on the vapor growing up process. In the initial stage, the vapor bubble expands in both radial and axial directions; while the growing up of vapor bubble in radial direction is impeded and the growing up along the axial direction speeds up when the diameter of the vapor bubble equals the tube diameter. The flow reversal will appear when the expanding velocity of the vapor bubble is larger than that of the flow velocity. The nucleation sites display different characteristics in that the detachment of vapor bubbles from the nucleation sites downstream is more frequent and the diameter of the vapor bubble is smaller. [Preview Abstract] |
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LZ.00029: Analysis of the plane Poiseuille flow of a wormlike micellar solution with shear banding Benjamin M. Marin-Santibanez, Jose Perez-Gonzalez, Lourdes de Vargas, Jean Paul Decruppe, Guadalupe Huelsz In this work a detailed study of the plane Poiseuille flow of a shear banding wormlike micellar aqueous solution is presented. The experiments were carried out at 27.5 \r{ }C under controlled pressure using a transparent flow cell, where simultaneous measurements of polarimetry, pressure drop and flow rate were performed in order to asses the flow stability. Particle image velocimetry was also used to analyze the flow kinematics upstream of the contraction. Five different regimes were observed in the flow curve, as well as the development and growth of shear bands right before the spurt. After the transition to the high shear branch, the flow became unstable and was composed by asymmetric shear bands of structured and isotropic fluid, which oscillated with respect to the zero-shear plane. Symmetric lip vortices were observed to grow and suddenly decrease under unstable flow conditions upstream of the contraction. The shear bands oscillated in the same way as upstream vortices with a frequency that increased along with flow rate. The oscillating flow upstream of the contraction arise from changes in the vortices size and produced jets or spurts of highly oriented material followed by recoiling of the micellar solution. [Preview Abstract] |
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LZ.00030: Experimental Study of Heavy Oil Displacement by Hot Water in Porous Media Abdullah Alajmi, Ridha Gharbi, Meshal Algharaib The injection of one fluid to displace another in a porous medium is the basis of many industrial processes such as Enhanced Oil Recovery (EOR). EOR applications are encouraged by high oil prices and growing oil demand. Therefore, performance prediction of EOR processes is of great importance to their success. Core flooding experiments are well known practices in the petroleum industry that provide economical means of determining the responses of reservoir rock and fluids to the driving mechanism responsible for production. Lab experiments provide both insight into the behavior of fluid displacements and data with which to test and calibrate numerical simulators. In this study, laboratory experiments were conducted in order to test the effectiveness of hot water injection to displace heavy oil from a given porous medium. The objective was to find the optimum design parameters in terms of injection temperature and hot water slug size that will yield the best performance. Analysis of these experiments has revealed the functional relationships between the scaling groups describing the displacement and the oil recovery obtained from such displacement. Results obtained from several design configurations are presented. These relationships can be used as a tool for the design of hot water injection to recover heavy oil. They also provide conditions under which a given design may yield better recovery performance. [Preview Abstract] |
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LZ.00031: Capillary Rise and Flow of Complex Liquids in Nanopores Patrick Huber, Simon Gruener We present measurements on the capillary rise (spontaneous imbibition) and pressure driven flow (forced imbibition) of liquids into silica monoliths (namely porous Vycor) permeated by tortuous pores with radii of 4.4nm (V10) and 3nm (V5) resp. The flow properties are studied as a function of the complexity of the building blocks of the liquids (water, n-alkanes and liquid crystals), of shear rate and temperature in the case of the liquid crystal. [Preview Abstract] |
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LZ.00032: Visualization of Velocity Profile on Separately Applied Hydrophobic and Hydrophilic Surfaces Natsuki Mukoshimizu, Takeshi Miyazaki, Katsuaki Morita, Hirotaka Sakaue A chemical flow control method using functional chemical is discussed. In our previous tests, we showed that separately applied hydrophobic and hydrophilic coatings with six different patterns on an ogive shape model could control the dropping speed by maximum 22 percent at the Reynolds number of 1.0E6. In the present study, we focused on the velocity profile on the coated surface. We use Fusso51 from Yukawa as hydrophobic coating and WaterX from Nishikinodo as a hydrophilic coating. Contact angles of these coatings are 130 degree and 5 degree, respectively, on anodized aluminum surfaces. These coatings are separately applied on a 2D profile. A hydrogen bubble technique is used to visualize its velocity profile related to the coatings. [Preview Abstract] |
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LZ.00033: Wall free energy based polynomial boundary conditions for non-ideal gases lattice boltzmann simulation Lin Liu, Taehun Lee Intermolecular forces between solid and liquid can be represented by the inclusion of the wall free energy in the expression of the total free energy for the bulk phases. We derived and investigated three types of polynomial (linear, quadratic, and cubic) wall free energy boundary conditions for the non-ideal gas lattice Boltzmann equation (LBE) method. Both static and dynamic drops on solid surfaces are examined. All the proposed boundary conditions are able to predict the equilibrium states very well in the moderate contact angle range by incorporating appropriate potential form of the intermolecular forces and the bounce-back rule that guarantees mass conservation for both static and dynamic cases. Simulations with different boundary conditions are carried out and the results are compared concerning the accuracy as well as the applicability of different boundary conditions. Numerical results show that the cubic boundary condition has the fastest spreading rate among the three types of the boundary conditions, while, due to the neglect of vapor-solid intermolecular forces and the highly elevated liquid density at the hydrophillic surface, the quadratic boundary condition demonstrates the slowest spreading rate. [Preview Abstract] |
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