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Physics of Fluids Collection


 
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Physics of Fluids : Selection of the divergence waves on a model v...

By: V. P. Reutov and G. V. Rybushkina

Description: The paper is concerned with the established regimes of generation of the divergence (quasistatic) waves on a model viscoelastic coating under a potential flow of an incompressible liquid. Parameters of the effective coating that consists of a strongly damped flexible plate supported by an extended spring foundation are evaluated using the condition of modeling the deformation of the viscoelastic layer of a rubberlike material in the available experiments. Th...

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Physics of Fluids : The influence of gravity on the steady propaga...

By: Andrew L. Hazel and Matthias Heil

Description: Motivated by discrepancies between recent bench-top experiments [ A. Juel and A. Heap, J. Fluid Mech. 572, 287 (2007) ] and numerical simulations [ A. L. Hazel and M. Heil, ASME J. Biomech. Eng. 128, 573 (2006) ] we employ computational methods to examine the effects of transverse gravity on the steady propagation of a semi-infinite, inviscid air finger into a two-dimensional elastic channel filled with a Newtonian fluid. The special case of propagation in a...

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Physics of Fluids : Evolution of neutral and charged droplets in a...

By: M. A. Fontelos, U. Kindelán, and O. Vantzos

Description: We study the evolution of drops of a very viscous and conducting fluid under the influence of an external electric field. The drops may be neutral or may be charged with some amount of electric charge. If both the external electric field and total drop charge are sufficiently small, then prolate spherical shapes develop according to Taylor’s observations. For sufficiently large charge and/or external field a self-similar conelike singularity develops in a me...

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Physics of Fluids : History force on an asymmetrically rotating bo...

By: Sukalyan Bhattacharya

Description: Experimental evidence shows that suspended particles preferentially migrate away from confining boundaries due to the effect of a shear flow. In this paper, we consider an asymmetric particle in Poiseuille flow and determine an inertial lift force which can contribute to the particle migration. Under the influence of Poiseuille flow in a slit pore, an arbitrary particle undergoes periodic rotation which is described by Jeffery’s orbit [ G. Jeffery, Proc. R. ...

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Physics of Fluids : Dynamics of prolate ellipsoidal particles in a...

By: P. H. Mortensen, H. I. Andersson, J. J. J. Gillissen, and B. J. Boersma

Description: The dynamical behavior of tiny elongated particles in a directly simulated turbulent flow field is investigated. The ellipsoidal particles are affected both by inertia and hydrodynamic forces and torques. The time evolution of the particle orientation and translational and rotational motions in a statistically steady channel flow is obtained for six different particle classes. The focus is on the influence of particle aspect ratio λ and the particle response...

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Physics of Fluids : An analysis of the far-field response to exter...

By: J. B›awzdziewicz and E. Wajnryb

Description: The leading-order far-field scattered flow produced by a particle in a parallel-wall channel under creeping-flow conditions has a form of the parabolic velocity field driven by a two-dimensional dipolar pressure distribution. We show that in a system of hydrodynamically interacting particles, the pressure dipoles contribute to the macroscopic suspension flow in a similar way as the induced electric dipoles contribute to the electrostatic displacement field. ...

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Physics of Fluids : Measurements of the steady streaming flow arou...

By: Florian Otto, Emmalee K. Riegler, and Greg A. Voth

Description: Granular particles vibrated in a fluid have been found to exhibit self-organization with attractive and repulsive interactions between the particles. These interactions have been attributed to the steady streaming flow around oscillating particles. Here we examine the steady streaming flow surrounding a vertically oscillating sphere using three-dimensional particle tracking velocimetry. We present measurements of the flow with the sphere far from boundaries,...

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Physics of Fluids : Taylor dispersion in polymerase chain reaction...

By: Jinkee Lee, Elejdis Kulla, Anuj Chauhan, and Anubhav Tripathi

Description: Polymerase chain reaction (PCR) is commonly used for a wide range of DNA applications such as disease detection, genetic fingerprinting, and paternity testing. The importance of PCR has led to an increased interest in performing PCR in a microfluidic platform with a high throughput while using very small DNA quantities. In this paper we solve convection-diffusion equations for the DNA and deoxynucleoside triphosphate (dNTP) under conditions suitable for PCR ...

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Physics of Fluids : A better nondimensionalization scheme for slen...

By: M. M. Weislogel, Y. Chen, and D. Bolleddula

Description: A scaling of the two-dimensional Laplacian operator is demonstrated for certain solutions (at least) to Poisson’s equation. It succeeds by treating the operator as a single geometric scale entity. The belated and rather subtle method provides an efficient assessment of the geometrical dependence of the problem and is preferred when practicable to the hydraulic diameter or term-by-term scaling for slender fully developed laminar flows. The improved accuracy f...

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Physics of Fluids : Mixing enhancement in electro-osmotic flows vi...

By: J. R. Pacheco

Description: The mixing of a passive tracer in a three-dimensional rectangular microchannel is studied numerically. A time-dependent electric field across a microchannel, filled with an electrolyte solution, is applied in order to realize a well-mixed state. Random perturbations to a time-periodic electric field are introduced in order to break the invariant tori of the system and to attain better mixing results. Two types of nonperiodic protocols are used to generate ch...

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Physics of Fluids : Circulation and energy of the leading vortex r...

By: L. Gao, S. C. M. Yu, J. J. Ai, and A. W. K. Law

Description: The gravity-driven starting jet characteristics over the range of Reynolds numbers from 1179 to 10 611 have been investigated using planar laser induced fluorescence and particle image velocimetry. Of the 17 cases investigated, pinch off for the leading vortex was found to appear at Reynolds number above 3000. For those cases involving pinch off, limiting values for the nondimensional circulation for the leading vortex could be identified at around 1.26 and ...

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Physics of Fluids : Chaotic scattering of two identical point vort...

By: Laust Tophøj and Hassan Aref

Description: A new numerical exploration suggests that the motion of two vortex pairs, with constituent vortices all of the same absolute circulation, displays chaotic scattering regimes. The mechanisms leading to chaotic scattering are different from the “slingshot effect” identified by Price [Phys. Fluids A 5, 2479 (1993) ] and occur in a different region of the four-vortex phase space. They may, in many cases, be understood by appealing to the solutions of the three-v...

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Physics of Fluids : Symmetry unbreaking in the shapes of perfect p...

By: Marcus Roper, Todd M. Squires, and Michael P. Brenner

Description: We study the shapes of perfect projectiles: Bodies of prescribed volume that are designed to suffer minimum fluid drag in steady flight. Perfect projectiles have a surprising property: Although the flow of fluid around the body of the projectile is fore-aft asymmetric at moderate flow speeds, the shape of the body that minimizes drag is nonetheless highly symmetrical. We show that perfect projectiles are weakly asymmetric and that their asymmetry grows with ...

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Physics of Fluids : Analytical solution for pulsatile viscous flow...

By: Sumeet Gupta, Dimos Poulikakos, and Vartan Kurtcuoglu

Description: We present here the analytical solution of transient, laminar, viscous flow of an incompressible, Newtonian fluid driven by a harmonically oscillating pressure gradient in a straight elliptic annulus. The analytical formulation is based on the exact solution of the governing fluid flow equations known as Navier–Stokes equations. We validate the analytical solution using a finite-volume computational fluid dynamics approach. As the analytical solution include...

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Physics of Fluids : Stability of a pair of co-rotating vortices wi...

By: Clément Roy, Nathanaël Schaeffer, Stéphane Le Dizès, and Mark Thompson

Description: The three-dimensional linear temporal stability properties of a flow composed of two corotating q-vortices (also called Batchelor vortices) are predicted by numerical stability analysis. As for the corresponding counter-rotating case, when the axial flow parameter is increased, different instability modes are observed and identified as a combination of resonant Kelvin modes of azimuthal wavenumbers m and m+2 within each vortex. In particular, we show that th...

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Physics of Fluids : Evolution of convective patterns in a binary-m...

By: B. L. Smorodin, B. I. Myznikova, and J. C. Legros

Description: A theoretical study has been made of the convective stability and developed heat transfer regimes in a horizontal, binary-mixture layer with negative Soret coupling. The system is under temperature gradient and finite-frequency vibration. Both analytical and numerical examinations are presented. The limiting case of long-wave disturbances is studied using the perturbation method. To find instability thresholds in the linear approximation the Floquet theory i...

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Physics of Fluids : On the linear and nonlinear development of Gör...

By: Tandiono, S. H. Winoto, and D. A. Shah

Description: The linear and nonlinear developments of Görtler vortices were experimentally investigated by means of hot-wire anemometer measurement. The wavelengths of the vortices were preset to be the most amplified using thin perturbation wires. Three different vortex wavelengths of 12, 15, and 20 mm were considered. These wavelengths were preserved downstream which confirm the prediction of the most amplified wavelength of Görtler vortices. The onset of the nonlinear...

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Physics of Fluids : Linear stability analysis of inclined two-laye...

By: M. Eletta Negretti, Scott A. Socolofsky, and Gerhard H. Jirka

Description: Two-layer stratified flows are commonly observed in geophysical and environmental contexts. At the interface between the two layers, both velocity shear and buoyancy interplay, resulting in various modes of instability. Results from a temporal linear stability analysis of a two-layer stratified exchange flow under the action of a mean advection are presented, investigating the effect of a mild bottom slope on the stability of the interface. The spatial accel...

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Physics of Fluids : Coherent flow states in a square duct

By: Håkan Wedin, Damien Biau, Alessandro Bottaro, and Masato Nagata

Description: The flow in a square duct is considered. Finite amplitude approximate traveling wave solutions, obtained using the self-sustaining-process approach introduced by Waleffe [Phys. Fluids 9, 883 (1997) ], are obtained at low to moderate Reynolds numbers and used as initial conditions in direct numerical simulations. The ensuing dynamics is analyzed in a suitably defined phase space. Only one among the traveling wave solutions found is capable of surviving for a ...

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Physics of Fluids : An asymptotic model for the Kelvin…Helmholtz a...

By: Yuri M. Shtemler, Michael Mond, Vladimir Cherniavskii, Ephim Golbraikh, and Yaakov Nissim

Description: The generalized Kelvin–Helmholtz (KH) and Miles mechanisms of the water wave generation by wind are investigated for two-layer piecewise linear model of the wind profile. It is shown by asymptotic expansions in small air-to-water density ratio that two mechanisms of the instability operate in quite different scales. Miles’ short waves are generated by weak winds, in particular, Miles’ regime is responsible for initiation of the instability at the minimum win...

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