Bulletin of the American Physical Society
2005 58th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 20–22, 2005; Chicago, IL
Session P1: Poster Session: General Fluid Dynamics |
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Chair: Kevin Cassel, Illinois Institute of Technology Room: Hilton Chicago International Ballroom North |
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P1.00001: Numerical Simulation on Hydrodynamics and Phase Change Associated with Multi-bubbles During Nucleate Boiling Xiao-Yong Luo, Ming-Jiu Ni, Alice Ying, Mohamed Abdou Development of predictive capability for hydrodynamics and phase change associated with multi-bubbles during nucleate boiling is essential to evaluate liquid wall protection schemes for various fusion chambers. This paper presents a numerical methodology for multiphase flow with phase change to help resolve feasibility issues encountered in the aforementioned fusion engineering fields. The numerical methodology is being conducted within the frame work of the incompressible flow with phase change. We present a new second order projection method, in conjunction with Approximate-Factorization techniques (AF method), for incompressible Navier-Stokes equations. The Crank-Nicholson method was used for the diffusion term to eliminate the numerical viscous stability restriction and 3rd order ENO scheme used for the convective term to guarantee the accuracy of the method. A four-level V cycle multigrid algorithm for pressure Poisson equation is used in order to decrease computation time. The level set method is used to capture the free surface of the flow and the deformation of the droplets accurately. This numerical investigation identifies the physics characterizing transient phase change and hydrodynamic interactions of the multi-bubbles during the nucleate boiling. [Preview Abstract] |
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P1.00002: Inner Temperature Scaling for Combined Convection Turbulent Boundary Layers Ashish Jaiswal, Xia Wang New inner length and temperature scalings are derived for the combined convection turbulent boundary layer. These new scaling are not obtained by the convectional dimensional analysis, but by considering the analogy of the driving and drag force between the momentum and thermal transport phenomena inside a turbulent boundary layer flow. The new thermal length scale and temperature scale are therefore derived using the known classical length and the velocity scale of the turbulent boundary layer. Using the experimental data from T. Tsuji and Y. Nagano (1990) and Blackwell (1972), it has been observed that the temperature profiles combine to form into a single curve when scaled by the new scalings. The inner temperature scaling derived are also compared with the existing natural convection scalings derived by George and Capp (1978) and the forced convection scaling by Wang and Castillo (2003). The existence of Grashoff Number and Stanton number in the inner scalings clearly indicates the possibility of domination of the buoyancy force or the possible effect of forced convection over the natural. A new dimensional less number has been found which consist of the Stanton number and the Richardson number based on which a clear judgment can be done on the type of convection that dominates the combined convection. Hence the new derived scalings appear to give more information regarding the type of flow. Efforts are made to verify the same scalings with a variety of thermal data. [Preview Abstract] |
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P1.00003: Experimental study of two-dimensional turbulence in sheared flow: initial results. Paul W. Fontana, John V. Ulmen, Martin Kearney-Fischer An experiment to study turbulence in quasi-two-dimensional flows with a controlled mean flow shear has been built. Experiments are underway to investigate the suppression of turbulent transport by sheared flow as seen in geostrophic flows and laboratory fusion plasmas. The apparatus, a two-dimensional Couette cell, uses a liquid film of dilute soap solution suspended freely in an annular channel with a rotating outer boundary. The channel is 7 cm wide with an average radius of 46.5 cm, and can be rotated at angular speeds exceeding 10 rad/s. Mean flow profiles will be presented showing the effect of air resistance on the flow. Turbulence is driven independently via electromagnetic forcing. The rate of turbulence injection can be varied continuously, and its spatial scale can be varied over an order of magnitude by selecting one of several arrays of NdFeB magnets. Diagnostics include particle imaging velocimetry, two-point laser Doppler velocimetry, and thickness measurements via reflection interferometry. Initial results and plans for upcoming measurements will be presented. [Preview Abstract] |
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P1.00004: Annular thin-film flows driven by azimuthal membrane tension variations. Leah Band, Sarah Waters, David Riley Thin films lining a rigid tube have been extensively studied assuming both constant and axially varying membrane tension at the film-core interface. Importantly though, the influence of azimuthal variations in the membrane tension has received far less attention. An annular geometry is considered. The outer boundary of the annulus is a rigid wall lined by two layers of viscous fluids. The layers are bounded by extensible membranes with specified variable membrane tensions. Nonlinear coupled evolution equations for the widths of the fluid layers are determined using thin-film asymptotics. For a range of membrane tensions, the steady state film profiles are determined and their linear stability examined. In addition, a pseudo-spectral method is used to obtain solutions to the full nonlinear evolution equations. For all variable membrane tensions there exists an unstable perturbation, in sharp contrast to the constant membrane tension case where all perturbations are stable. These results will be interpreted in the context of plaque growth within arteries. [Preview Abstract] |
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P1.00005: Scaling Immiscible Displacements in Porous Media with Horizontal Wells Ridha Gharbi, Meshal Algharaib The displacement of one fluid by another in a porous medium is the basis of many industrial processes such as Enhanced Oil Recovery (EOR) and the remediation of contaminated aquifers. In recent years, the petroleum industry has experienced a rapid increase in using horizontal wells in these displacement processes. In this study, a general method is presented to scale immiscible displacements of oil by water through homogeneous reservoirs produced by horizontal wells. Following a rigorous procedure of inspectional analysis, results show that there are five independent dimensionless scaling groups that describe immiscible displacement of oil by water in two-dimensional, homogeneous, anisotropic porous medium with constant porosity and dip angle. These represent the minimum number of dimensionless groups which are required to scale the displacement. Fine-mesh numerical simulations were then performed in order to reveal the functional relationships between the scaling groups describing the displacement and the fractional oil recovery obtained from such displacement. The results obtained from several well configurations will be presented. These relationships can be used as a quick prediction tool for the fractional oil recovery for any combinations of the scaling groups, thus eliminating the need for the expensive fine-mesh simulations. These results have potential applications in modeling immiscible displacements and in the scaling of laboratory displacements to field conditions. [Preview Abstract] |
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P1.00006: Dynamic simulation of dielectrophoresis in colloidal suspension Xianjin Jiang, Nadine Aubry, Pushpendra Singh We have developed a molecular-dynamics-like method to simulate the behavior of dielectric particles suspension in electrorheological fluid subjected to both uniform and nonuniform electric fields. In this method, the force acting on the particles is calculated by differentiating the electrostatic energy with respect to the position, and the energy is computed with multiple image method. The results show that considering dielectrophoretic force (DEP) force only is not enough for the simulation of particle motion when the suspension is subjected to nonuniform electric field since particle-particle interactions are ignored. The DEP-only approximation becomes more limited for the study of particles very close to each other. Our new method accounts for both particle-field (DEP) and particle-particle interactions under near- and far-field conditions. [Preview Abstract] |
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P1.00007: An experimental model for solid fracture Shehla Arif, Adrian Staicu, Sascha Hilgenfeldt A two-dimensional monodisperse dry liquid foam confined in a rectangular-channel Hele-Shaw cell driven by compressed air is used as a model system to study fracture and crack propagation in a solid. As a yield-stress material composed of mm-sized bubbles, the foam allows studies of failure at both the macroscopic (channel) and microscopic (bubble) scales. At smaller driving forces, a finger-like structure evolves emulating quasi-static crack growth. Higher driving forces cause fast rupture of consecutive films, drawing parallels with dynamic crack propagation. [Preview Abstract] |
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P1.00008: The de-pinning transition of periodically vibrated sessile drops. Craig Caylor, Colin Campbell, Viatcheslav Berejnov, Robert Thorne We studied dynamics of the shape and contact line of sessile drops under horizontal linear periodic vibrations. We observed a transition between two general regimes of drop behavior. The first is controlled by the contact angle hysteresis, when the drop's contact line remains pinned by the substrate. In this case, only the drop shape varies with respect to the amplitude and frequency of vibrations. Beyond a critical acceleration, the drop's contact line de-pins partially or completely and the drop's dynamics transfer to a second regime. In this regime the contact line dynamics and the advancing and receding contact angles strongly depend on the instantaneous velocity of the substrate. Within this second regime i) only the receding angle is strongly affected by the vibrations, ii) the contact angle hysteresis becomes dynamical and depends on the vibration characteristics. [Preview Abstract] |
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P1.00009: Behavior of multiple bubbles in a row under ultrasonic pressure field Ichiro Ueno, Tatsunori Kojo The present paper discusses behaviors of a single or multiple bubbles exposed to ultrasonic vibration in water under isothermal condition. In the single bubble case, excitation of the surface wave over the free surface or shape oscillation with high-order mode is indicated through the observation by use of the high-speed camera. The behavior depends upon the amplitude of the vibration. In the case of multiple bubbles, the authors focus upon a system in which the ultrasonic pressure field is irradiated to the bubbles in a row from the top; the propagation direction of the pressure field is parallel to the row. The effect of the preceding bubble upon the behavior of the following bubbles is presented. [Preview Abstract] |
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P1.00010: Shear Induced diffusivity of non-spherical particles Mauricio Lopez, Michael Graham The shear induced diffusivity of non-spherical particles is studied both experimentally and numerically. Experimentally, the shear induced diffusivity of fractal aggregates is obtained by measuring the width of the interface between dyed and non-dyed suspensions flowing adjacently in a microfluidic channel using Leveque scaling. Numerical calculations of the shear induced diffusivity of rods, ``bucky balls'' and branched particles are performed by integrating the mean square displacement upon collision of two particles over all possible collisions. Particle trajectories are calculated using rigid body dynamics along with the Stokesian Dynamics method, and a short range repulsive force between beads belonging to different particles. The effect of the range of the repulsive force on the shear induced diffusivity is studied for all the particles used in our calculations. It is found that from the particles tested rods have the smallest shear induced diffusivity, while open branched particles have the largest. The increase in diffusivity is especially large in the vorticity direction. [Preview Abstract] |
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P1.00011: Experimental study of scale-dependent droplet clustering in turbulence E.W. Saw, R.A. Shaw, S. Ayyalasomayajula, P.Y. Chuang, A. Gylfason, Z. Warhaft To evaluate the dependence of inertial particle clustering on turbulence parameters we have investigated the spatial distribution of particles in laboratory turbulence. The experimental facility is an active-grid wind tunnel, generating approximately homogeneous, isotropic turbulence with $R_\lambda$ in the range of 300 to 900. Under statistically stationary conditions droplets are injected into the flow and downstream their diameter, longitudinal speed, and time of arrival are measured at a point with a phase Doppler interferometer. The resulting particle pair correlation functions $\eta(r)$ show droplet clustering increasing with decreasing spatial scale $r$ and with increasing Stokes number as expected from theoretical and computational work. Specifically, the particle pair correlation function $\eta(r)$ has a negative power law dependence on $r$ for $r < 10 r_k$, where $r_k$ is the Kolmogorov microscale. Furthermore, the power-law exponent increases with the dimensionless droplet Stokes number, defined as $St=(1/18)(\rho_p/\rho)(d/r_k)^2$ for particle diameter $d$. These experiments at high Reynolds numbers provide a link to geophysical systems where inertial droplet clustering is thought to be of relevance, such as atmospheric clouds and the rate of rain formation. [Preview Abstract] |
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P1.00012: Bifurcation, stability and nonlinear interaction of gravity-capillary solitary waves Boguk Kim, Triantaphyllos R. Akylas Gravity-capillary plane solitary waves are known to bifurcate in the form of wavepackets with specific carrier wavenumbers at which the phase speed attains an extremum. Fully nonlinear branches of such solitary waves are obtained via a numerical continuation procedure, and the stability of each bifurcation branch is discussed. Two kinds of stabilities are considered, longitudinal stability (Lstability) under perturbations along the dominant wave propagation direction and transverse stability (Tstability) under perturbations along the transverse direction to wave propagation. Tstability, especially, results in the formation of fully localized gravity-capillary solitary waves, commonly referred to as lumps. Lumps are surprisingly stable coherent structures and follow the same bifurcation scenario as that of plane solitary waves. The formation of lumps and their nonlinear interactions are presented by using unsteady numerical simulations. The outline of the video presentation is as follows: Bifurcation of Benjamin plane solitary waves; Transverse instability of Benjamin plane solitary waves and formation of lumps; Bifurcation of Benjamin lumps; Nonlinear interaction of Benjamin lumps; Description of numerical method. [Preview Abstract] |
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P1.00013: Defect Dynamics in Hexachaos Will Brunner, Jonathan McCoy, Werner Pesch, Eberhard Bodenschatz We present a new state of spatio-temporal chaos in inclined layer convection which we term hexachaos. We create this state when we break the symmetry of hexagons in non-Boussinesq convection by inclining the fluid layer by 5$^{\circ}$ from horizontal. This causes one of the three modes of the hexagonal pattern (that parallel to the tilt direction) to be preferred, while the two oblique modes are weakened and their amplitudes become chaotic. To better understand the dynamics of this system, we study topological defects it contains. We separate the three modes by Fourier demodulation, and locate dislocations in each mode separately. We then group dislocations pairwise into either penta-hepta defects (PHDs) or new entities which we term same-mode complexes (SMCs.) We then observe the various reactions which these defects participate in, and derive statistics of these reactions. We observe that SMCs are destroyed at rates proportional to their density, as opposed to PHDs which are destroyed proportional to their density squared. We show that this difference is consistent with the mass action law applied to the respective reaction equations, and speculate on the similarity to results found in other hexagonal systems with broken symmetry. [Preview Abstract] |
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P1.00014: Detached-Eddy Simulation of Wind-Induced Ventilation to Control Indoor Thermal Environments Takamasa Hasama, Shinsuke Kato, Ryozo Ooka There are numerous examples of computational fluid dynamics (CFD) being used to analyze wind-induced ventilation in buildings. Ventilation properties are affected not only by the mean flow but also turbulent flow characteristics, resulting in complicated flowfields around building openings. We therefore have to use a CFD method that is able to precisely simulate the turbulence phenomena. Detached-eddy simulations (DES) are remarkable in terms of computing cost performance, and their application is expected to building environmental analysis. In this paper, to examine the applicability of DES to building ventilation analysis, DES and large-eddy simulations (LES) were performed on a flow around a building having a single-sided opening. We also examined the applicability of DES to indoor thermal environmental analysis and made simulations of an anisothermal flowfield with a heat source on the same analysis model. Three types of calculation cases, namely; 1) Reference LES calculation with fine grid, 2) LES calculation with coarse grid, and 3) DES calculation with coarse grid, were performed. We clarified the wind and temperature fluctuation characteristics and heat flux around the opening, and also analyzed DES characteristics of the anisothermal flowfield. [Preview Abstract] |
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P1.00015: Passive mixing in a wide microchannel using surface patterns Vishwanath Somashekar, Michael Olsen, Mark Stremler Passive mixing is typically achieved on the microscale by driving fluid through microchannels with geometries that either (1) produce strong secondary flows or (2) split and recombined the fluid multiple times. We present a microchannel design that incorporates both of these approaches into a single channel. Our design uses oblique surface grooves on one channel wall to generate strong secondary flows at low Reynolds numbers. The surface groove pattern is inspired by the herringbone pattern of Stroock et al. (2002), who demonstrate good mixing results in a channel with aspect ratio near one. We extend this approach by tiling the wall of a high-aspect- ratio channel with several parallel herringbone patterns, which generate a number of parallel counter-rotating regions in the flow. Alternating the surface patterns in the axial direction causes interaction of these parallel streams in a way that is similar to splitting and recombining multiple channels. We demonstrate this approach to passive mixing in a PDMS microchannel that is 50~$\mu$m deep and~2500 $\mu$m wide. Mixing is characterized experimentally over a range of Reynolds numbers using a phenolphthalein reaction. At $Re = 0.8$, fluid is mixed across the entire channel width after 40~mm. [Preview Abstract] |
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P1.00016: Topological chaos in spatially periodic mixers Matt Finn, Jean-Luc Thiffeault, Emmanuelle Gouillart In many industrial fluid stirring processes it is desirable to produce a high stretching rate of material lines. In two-dimensional flows this stretching rate is given by the {\it topological entropy} of the flow. {\it Topological Chaos} offers a way of constructing flows that have a rigorous topological entropy lower bound that is robust against changes in fluid properties and the exact details of the apparatus geometry. We examine topologically chaotic fluid advection in two-dimensional flows where either or both directions are spatially periodic. Our study is motivated by the ubiquity of periodic boundary conditions for prototype flows in the literature, and also by some rare examples of actual flows that exhibit spatial periodicity. For nonperiodic domains, it is already known how to obtain topological entropy lower bounds for such flows by analysing the braid formed by the stirring apparatus using the Bestvina--Handel train-track algorithm. However, in spatially periodic flows, in addition to usual braiding motions, there are new motions corresponding to stirring rods traversing the periodic directions. This leads to the study of braids on the cylinder and the torus. We describe how the train-track algorithm may be applied in such cases to produce topological entropy lower bounds. Through analysis and numerical simulation we show how periodic boundary conditions are of great assistance in creating chaos. We also analyse the well-known sine-flow but from a new topological perspective. [Preview Abstract] |
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P1.00017: Investigation of dusty plasma liquid viscosity Iya Shakhova, Andrey Gavrikov, Olga Vaulina, Alexander Ivanov, Nazar Vorona, Oleg Petrov, Vladimir Fortov The series of experiments aimed at investigation of dusty plasma shear viscosity has been carried out by us. We have concerned ourselves with laminar flow of dusty plasma caused by laser radiation pressure. Experimental dependencies of flow velocity profile on value of external influence and plasma generating gas pressure have been obtained. Based on these data shear viscosity coefficient dependencies on laser beam power have been got, the dependencies being different for different background gas pressure Dusty plasma liquid represents a multiphase medium with screened Coulomb interaction between solid grains. This results in the complexity of experimental data interpretation. It should be mentioned that the use of Navier-Stokes equation for analysis of flow necessitates its vindication, for the equation itself is not suitable for parting momentum transfer by different ways and for unambiguous separating of viscosity caused by dusty component. In this paper we report about the study of momentum transfer in laminar flow of dusty plasma liquid. [Preview Abstract] |
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P1.00018: Wind tunnel experiment for visible plume from mechanical draft cooling tower Takenobu Michioka, Ayumu Sato, Kouichi Sada As moist air leaves a wet cooling tower, it mixes with cooler atmospheric air. This mixing generates a visible plume, which is the condensation of a fraction of the water vapor, and the visible plume produces some significant atmospheric effects, such as the obstruction to visibility and ice formation on the ground. It is therefore of importance to predict the visible plume region from the mechanical draft cooling tower in environmental impact assessment. We developed a method for a wind tunnel experiment to predict a visible plume region from a mechanical-draft cooling tower. The diffusions of water vapor and heat emitted from the cooling tower in the wind tunnel are estimated using a tracer gas. A moist plume-induced fog is assumed to be generated whenever the instantaneous water vapor mixing ratio estimated using the concentration of the tracer gas at measured points is larger than the inferred saturation water vapor mixing ratio. To confirm the validity of the present method, the results in the wind tunnel experiments are compared with the observations obtained at the mechanical draft cooling tower of the Benning Road plant. The results show that the visible plume length and height are nearly in agreement with the observations and the present method has capability to predict the visible plume region from the cooling tower. [Preview Abstract] |
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P1.00019: Retrieval of Micro scale Atmospheric Flow Structures from Dual-Doppler Lidar Data Quanxin Xia , Ching-Long Lin, Ronald Calhoun, Rob K. Newson In the Joint Urban 2003 atmospheric field experiment held in Oklahoma City, two coherent Doppler lidars were deployed to gain new insights into the boundary layer transport processes of contaminants in and around cities. That provided the opportunity to evaluate the accuracy of the four-dimensional variational data assimilation (4DVAR) method designed for single-lidar data retrieval. This work is to determine the fidelity of the data retrieved from the 4DVAR and assess model errors. With the availability of two Doppler lidar data sets, we perform 4DVAR analysis on radial velocity data measured from one lidar system. The retrieved velocity field is then used to construct radial velocity which can subsequently be compared with those measured from the second system for the error analysis. The building data is also utilized to interpret the retrieved structures. [Preview Abstract] |
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P1.00020: Capillary forces between non-spherical colloids Ernst van Nierop, Sascha Hilgenfeldt Uncharged, spherical colloidal particles at an air-water interface experience no significant interaction forces if their radii are below a critical size. However, strong attraction and repulsion can still be observed when the shape of the particles deviates even slightly from an ideal sphere. We show that $nm$-scale deviations from sphericity on $\mu m$-sized particles lead to interaction energies in excess of thermal energies, resulting in positional and orientational ordering at the interface. Dendritic or lattice-like rafts are observed, the latter showing hexagonal positional and herringbone orientational order. [Preview Abstract] |
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P1.00021: Mechanoluminescence from Acoustic Cavitation Nathan Eddingsaas, Kenneth Suslick The external effects of acoustic cavitation- the formation, expansion, and implosive collapse of bubbles in liquids irradiated with ultrasound- include turbulent flow, shock waves, and microjetting. To study these effects we have looked at mechanoluminescence (ML): light produced during any mechanical action on a solid. We report for the first time the ML of sucrose and resorcinol induced by acoustic cavitation in alkanes. The spectra of ML induced by cavitation resemble other sources of ML but with more intense gas discharge relative to the crystal luminescence. It is known that as the strength of the mechanical action on the solid is increased the intensity of the gas discharge increases; this gives evidence of the extreme external effects of cavitation. We have also observed other discharge products not seen before in ML including CH, C2, and CO (when oxygen is present). The effect of liquid vapor pressure (VP) has also been studied; as lower VP liquids are used the ML intensity of the gas discharge increases. In high VP liquids no helium gas discharge is observed, but with very low VP liquids the gas discharge is very intense. [Preview Abstract] |
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