scholarly journals Combined electrokinetic and shear flows control colloidal particle distribution across microchannel cross-sections

Soft Matter ◽  
2021 ◽  
Author(s):  
Varun Lochab ◽  
Shaurya Prakash
Keyword(s):  
Shear Flow ◽  
Cross Sections ◽  
Lift Force ◽  
Shear Flows ◽  
Colloidal Particle ◽  
Particle Distribution ◽  
Particle Migration ◽  
Flow Parameters

We quantify and investigate the effects of flow parameters on the extent of colloidal particle migration and the corresponding electrophoresis-induced lift force under combined electrokinetic and shear flow.

Chirality-specific lift forces of helix under shear flows

2017 ◽  
Vol 31 (11) ◽  
pp. 1750117 ◽  
Author(s):  
Qi-Yi Zhang ◽  
Kai-Yan Hu ◽  
Wen-Yan Yang
Keyword(s):  
Shear Flow ◽  
Lift Force ◽  
Shear Flows ◽  
Analytical Formula ◽  
Flow Experience ◽  
Pitch Length ◽  
Simulation Results ◽  
Lift Forces ◽  
Physical Reasons ◽  
Helix Geometry

Chiral objects in a shear flow experience a chirality-specific lift force. Shear flows past helices in low Reynolds number regime are studied by a highly efficient iterative method, based on the analytical solution of a sphere in uniform flow. The chirality-specific lift forces in the vorticity direction experienced by helices are dominated by a set of helix geometry parameters: helix radius ([Formula: see text]), pitch length (b), number of turns and helix phase angle. Its analytical formula is firstly given. The chirality-specific forces are the physical reasons for the chiral separation of helices in shear flow. Our results are qualitatively in agreement with the simulation results and well supported by the latest experimental observations.

Propagation of internal gravity waves in fluids with shear flow and rotation

1967 ◽  
Vol 30 (3) ◽  
pp. 439-448 ◽  
Author(s):  
Walter L. Jones
Keyword(s):  
Angular Momentum ◽  
Shear Flow ◽  
Gravity Waves ◽  
Shear Flows ◽  
Internal Gravity Waves ◽  
Vertical Transport ◽  
Wave Frequency ◽  
Slow Rotation ◽  
Critical Levels ◽  
Rotating System

In a rotating system, the vertical transport of angular momentum by internal gravity waves is independent of height, except at critical levels where the Doppler-shifted wave frequency is equal to plus or minus the Coriolis frequency. If slow rotation is ignored in studying the propagation of internal gravity waves through shear flows, the resulting solutions are in error only at levels where the Doppler-shifted and Coriolis frequencies are comparable.

scholarly journals Turbulent drag reduction by polymer additives in parallel-shear flows

2017 ◽  
Vol 827 ◽  
Author(s):  
Bayode E. Owolabi ◽  
David J. C. Dennis ◽  
Robert J. Poole
Keyword(s):  
Drag Reduction ◽  
Cross Sections ◽  
Shear Flows ◽  
Extensional Flow ◽  
Relaxation Times ◽  
Weissenberg Number ◽  
Mechanical Degradation ◽  
Turbulent Drag Reduction ◽  
Time Resolved ◽  
Turbulent Drag

In this study, we experimentally investigate the turbulent drag-reduction (DR) mechanism in flow through ducts of circular, rectangular and square cross-sections using two grades of polyacrylamide in aqueous solution having different molecular weights and various semidilute concentrations. Specifically, we explore the relationship between drag reduction and fluid elasticity, purposely exploiting the mechanical degradation of polymer molecules to vary their rheological properties. We also obtain time-resolved velocity data for various DR levels using particle image velocimetry and laser Doppler velocimetry. Elasticity is quantified via relaxation times determined from uniaxial extensional flow using a capillary breakup apparatus. A plot of DR against Weissenberg number ($Wi$) is found to approximately collapse the data, with the onset of DR occurring at $Wi\approx 0.5$ and the maximum drag-reduction asymptote being approached for $Wi\gtrsim 5$. Thus quantitative predictions of DR in a range of shear flows can be made from a single measurable material property of a polymer solution, at least for this particular flexible linear polymer.

scholarly journals The lift on a small sphere in a slow shear flow

1965 ◽  
Vol 22 (2) ◽  
pp. 385-400 ◽  
Author(s):  
P. G. Saffman
Keyword(s):  
Shear Flow ◽  
Velocity Profile ◽  
Kinematic Viscosity ◽  
Lift Force ◽  
Flow Direction ◽  
Functional Dependence ◽  
Small Sphere ◽  
Translation Velocity ◽  
Parabolic Velocity Profile ◽  
Direction Opposite

It is shown that a sphere moving through a very viscous liquid with velocity V relative to a uniform simple shear, the translation velocity being parallel to the streamlines and measured relative to the streamline through the centre, experiences a lift force 81·2μVa2k½/v½ + smaller terms perpendicular to the flow direction, which acts to deflect the particle towards the streamlines moving in the direction opposite to V. Here, a denotes the radius of the sphere, κ the magnitude of the velocity gradient, and μ and v the viscosity and kinematic viscosity, respectively. The relevance of the result to the observations by Segrée & Silberberg (1962) of small spheres in Poiseuille flow is discussed briefly. Comments are also made about the problem of a sphere in a parabolic velocity profile and the functional dependence of the lift upon the parameters is obtained.

An Application of Distributed Computing to the Finite Element Investigation of Lift Force on a Freely-Rotating Sphere in Simple Shear Flow

1999 ◽  
Author(s):  
Gustavo C. Buscaglia ◽  
Hugo E. Ferrari ◽  
Pablo M. Carrica ◽  
Enzo A. Dari
Keyword(s):  
Finite Element ◽  
Shear Flow ◽  
Simple Shear ◽  
Lift Force ◽  
Cluster Computing ◽  
Low Cost ◽  
Lift Coefficient ◽  
Angular Acceleration ◽  
Spherical Particles ◽  
Simple Shear Flow

Abstract An application of “cluster computing” in finite element CFD is reported, demonstrating the feasibility of solving relevant 3D problems on low-cost architectures (PC’s connected by fast Ethernet network). The main ingredients of our implementation are described. The results concern the lift force on a solid particle in simple shear flow. It is shown that, if the particle is allowed to rotate freely about its center, the self-established rotation significantly alters the lift coefficient. in particular, the lift force points away from a wall for any Re (≤ 100), while if the particle does not rotate the lift changes sign. Suitable estimates for the typical time involved in the angular acceleration of solid spherical particles are derived.

scholarly journals Numerical simulations of vorticity banding of emulsions in shear flows

Soft Matter ◽  
2020 ◽  
Vol 16 (11) ◽  
pp. 2854-2863 ◽  
Author(s):  
Francesco De Vita ◽  
Marco Edoardo Rosti ◽  
Sergio Caserta ◽  
Luca Brandt
Keyword(s):  
Shear Flow ◽  
Numerical Simulations ◽  
Effective Viscosity ◽  
Shear Flows ◽  
Viscosity Ratio ◽  
Low Viscosity

Emulsion under shear flow can exhibit banded structures at low viscosity ratio. When coalescence is favoured, it can stabilize bands generated by migration of droplets. The reduction of the total surface results in a lower effective viscosity state.

Responses of human adipose-derived stem cells to interstitial level of extremely low shear flows regarding differentiation, morphology, and proliferation

Lab on a Chip ◽  
2017 ◽  
Vol 17 (12) ◽  
pp. 2115-2124 ◽  
Author(s):  
Sung-Hwan Kim ◽  
Kihoon Ahn ◽  
Joong Yull Park
Keyword(s):  
Stem Cells ◽  
Shear Stress ◽  
Shear Flow ◽  
Shear Flows ◽  
Stress Gradient ◽  
Adipose Derived Stem Cells ◽  
Shear Stress Gradient ◽  
Low Shear

We developed a shear stress-gradient chip, which mimickedin vivointerstitial level of flow. With this system, hASCs' quantitative responses to the interstitial level of shear flow are identified.

The analysis of self-diffusion and migration of rough spheres in nonlinear shear flow using a traction-corrected boundary element method

2008 ◽  
Vol 598 ◽  
pp. 267-292 ◽  
Author(s):  
MARC S. INGBER ◽  
SHIHAI FENG ◽  
ALAN L. GRAHAM ◽  
HOWARD BRENNER
Keyword(s):  
Boundary Element Method ◽  
Shear Flow ◽  
Boundary Element ◽  
Particle Migration ◽  
Self Diffusion ◽  
Centre Of Gravity ◽  
Particle Pairs ◽  
And Migration ◽  
Nonlinear Shear ◽  
Element Method

The phenomena of self-diffusion and migration of rough spheres in nonlinear shear flows are investigated using a new traction-corrected boundary element method (TC-BEM) in which the near-field asymptotics for the traction solution in the interstitial region between two nearly touching spheres is seamlessly coupled with a traditional direct boundary element method. The TC-BEM is extremely accurate in predicting particle trajectories, and hence can be used to calculate both the particle self-diffusivity and a newly defined migration diffusivity for dilute suspensions. The migration diffusivity is a function of a nonlinearity parameter characterizing the shear flow and arises from the net displacement of the centre of gravity of particle pairs. This net displacement of the centre of gravity of particle pairs does not occur for smooth particles, nor for rough particles in a linear shear flow. An explanation is provided for why two-particle interactions of rough spheres in a nonlinear shear flow result in particle migration.

scholarly journals Study on Lift Force acting on Single Drops in Linear Shear Flows

2007 ◽  
Vol 2 ◽  
pp. 55-62 ◽  
Author(s):  
Kohei OGAWA ◽  
Win MYINT ◽  
Shigeo HOSOKAWA ◽  
Akio TOMIYAMA
Keyword(s):  
Lift Force ◽  
Shear Flows ◽  
Linear Shear

The breaking of transient inertio-gravity waves in a shear flow using the Gaussian beam approximation

2014 ◽  
Vol 759 ◽  
pp. 676-700 ◽  
Author(s):  
C. Rodas ◽  
M. Pulido
Keyword(s):  
Shear Flow ◽  
Gaussian Beam ◽  
Ray Tracing ◽  
Gravity Waves ◽  
Convective Instability ◽  
Shear Flows ◽  
Computational Cost ◽  
Dynamical Instability ◽  
Initial Time ◽  
Instability Criterion

AbstractThe propagation of transient inertio-gravity waves in a shear flow is examined using the Gaussian beam formulation. This formulation assumes Gaussian wavepackets in the spectral space and uses a second-order Taylor expansion of the phase of the wave field. In this sense, the Gaussian beam formulation is also an asymptotic approximation like spatial ray tracing; however, the first one is free of the singularities found in spatial ray tracing at caustics. Therefore, the Gaussian beam formulation permits the examination of the evolution of transient inertio-gravity wavepackets from the initial time up to the destabilization of the flow close to the critical levels. We show that the transience favours the development of the dynamical instability relative to the convective instability. In particular, there is a well-defined threshold for which small initial amplitude transient inertio-gravity waves never reach the convective instability criterion. This threshold does not exist for steady-state inertio-gravity waves for which the wave amplitude increases indefinitely towards the critical level. The Gaussian beam formulation is shown to be a powerful tool to treat analytically several aspects of inertio-gravity waves in simple shear flows. In more realistic shear flows, its numerical implementation is readily available and the required numerical calculations have a low computational cost.

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