Axisymmetric two-sphere sedimentation in a shear thinning viscoelastic fluid: Particle interactions and induced fluid velocity fields

2007 ◽  
Vol 51 (6) ◽  
pp. 1343-1359 ◽  
Author(s):  
Emilie Verneuil ◽  
Ronald J. Phillips ◽  
Laurence Talini
Keyword(s):  
Viscoelastic Fluid ◽  
Fluid Velocity ◽  
Shear Thinning ◽  
Velocity Fields ◽  
Fluid Particle ◽  
Particle Interactions

scholarly journals Undulatory swimming in shear-thinning fluids: experiments with Caenorhabditis elegans

2014 ◽  
Vol 758 ◽  
Author(s):  
D. A. Gagnon ◽  
N. C. Keim ◽  
P. E. Arratia
Keyword(s):  
Caenorhabditis Elegans ◽  
Fluid Velocity ◽  
Shear Thinning ◽  
Velocity Fields ◽  
Swimming Behaviour ◽  
Kinematic Data ◽  
Shear Thinning Fluids ◽  
Fluid Environment ◽  
Micro Organisms ◽  
Undulatory Swimming

AbstractThe swimming behaviour of micro-organisms can be strongly influenced by the rheology of their fluid environment. In this article, we experimentally investigate the effects of shear-thinning (ST) viscosity on the swimming behaviour of an undulatory swimmer, the nematode Caenorhabditis elegans. Tracking methods are used to measure the swimmer’s kinematic data (including propulsion speed) and velocity fields. We find that ST viscosity modifies the velocity fields produced by the swimming nematode but does not modify the nematode’s speed and beating kinematics. Velocimetry data show significant enhancement in local vorticity and circulation and an increase in fluid velocity near the nematode’s tail. These findings are compared with recent theoretical and numerical results.

Two Algorithms for Solving Coupled Particle Dynamics and Flow Field Equations in Two-Phase Flows

2010 ◽  
Author(s):  
R. Kamali ◽  
S. A. Shekoohi
Keyword(s):  
Flow Field ◽  
Particle Dynamics ◽  
Fluid Particle ◽  
Navier Stokes ◽  
Test Cases ◽  
Particle Interactions ◽  
Field Equations ◽  
Two Phase ◽  
Coupled Equations ◽  
Solution Accuracy

Two methods for solving coupled particle dynamics and flow field equations simultaneously by considering fluid-particle interactions to simulate two-phase flow are presented and compared. In many conditions, such as magnetic micro mixers and shooting high velocity particles in fluid, the fluid-particle interactions can not be neglected. In these cases it is necessary to consider fluid-particle interactions and solve the related coupled equations simultaneously. To solve these equations, suitable algorithms should be used to improve convergence speed and solution accuracy. In this paper two algorithms for solving coupled incompressible Navier-Stokes and particle dynamics equations are proposed and their efficiencies are compared by using them in a computer program. The main criterion that is used for comparison is the time they need to converge for a specific accuracy. In the first algorithm the particle dynamics and flow field equations are solved simultaneously but separately. In the second algorithm in each iteration for solving flow field equations, the particle dynamics equation is also solved. Results for some test cases are presented and compared. According to the results the second algorithm is faster than the first one especially when there is a strong coupling between phases.

scholarly journals Diffusiophoresis in Suspensions of Charged Soft Particles

2020 ◽  
Vol 4 (3) ◽  
pp. 30
Author(s):  
Wei C. Lin ◽  
Huan J. Keh
Keyword(s):  
Charge Density ◽  
Volume Fraction ◽  
Fluid Velocity ◽  
Hard Core ◽  
Unit Cell ◽  
Soft Particle ◽  
Particle Interactions ◽  
Porous Shell ◽  
Screening Parameter ◽  
Soft Particles

The diffusiophoresis in a suspension of charged soft particles in electrolyte solution is analyzed. Each soft particle is composed of a hard core of radius r0 and surface charge density σ and an adsorbed fluid-penetrable porous shell of thickness a−r0 and fixed charge density Q. The effect of particle interactions is considered by using a unit cell model. The ionic concentration, electric potential, and fluid velocity distributions in a unit cell are solved as power expansions in σ and Q, and an explicit formula for the diffusiophoretic velocity of the soft particle is derived from a balance between the hydrodynamic and electrostatic forces exerted on it. This formula is correct to the second orders of σ and Q and valid for arbitrary values of κa, λa, r0/a, and the particle volume fraction of the suspension, where κ is the Debye screening parameter and λ is the reciprocal of a length featuring the flow penetration into the porous shell. The effects of the physical characteristics and particle interactions on the diffusiophoresis (including electrophoresis and chemiphoresis) in a suspension of charged soft particles, which become those of hard particles and porous particles in the limits r0=a and r0=0, respectively, are significant and complicated.

Flow Field Analysis of Dielectrophoretically-Suspended Particles

2007 ◽  
Author(s):  
Stuart J. Williams ◽  
Steven T. Wereley
Keyword(s):  
Electric Fields ◽  
Particle Image ◽  
Fluid Velocity ◽  
Microfluidic Channel ◽  
Velocity Fields ◽  
Field Analysis ◽  
Tracer Particles ◽  
Image Velocimetry ◽  
Flow Field Analysis ◽  
Complete Investigation

Understanding the fluid dynamics around a particle in suspension is important for a complete investigation of many hydrodynamic phenomena, including microfluidic models. A novel tool that has been used to analyze fluid velocity fields in microfluidics is micro-resolution particle image velocimetry (μPIV) [1]. Dielectrophoresis (DEP) is a technique that can translate and trap particles by induced polarization in the presence of nonuniform electric fields. In this paper, DEP has been used to capture and suspend a single 10.1μm diameter spherical particle in a microfluidic channel. μPIV is then used with smaller tracer particles (0.5μm) to investigate the hydrodynamics of fluid flow past the trapped particle.

scholarly journals Simultaneous X-ray Video-Fluoroscopy and Pulsed Ultrasound Velocimetry Analyses of the Pharyngeal Phase of Swallowing of Boluses with Different Rheological Properties

Dysphagia ◽  
2020 ◽  
Vol 35 (6) ◽  
pp. 898-906
Author(s):  
Waqas M. Qazi ◽  
Olle Ekberg ◽  
Johan Wiklund ◽  
Rashid Mansoor ◽  
Mats Stading
Keyword(s):  
Rheological Properties ◽  
Shear Viscosity ◽  
Fluid Velocity ◽  
Shear Thinning ◽  
Invasive Technique ◽  
X Ray ◽  
Non Invasive ◽  
Constant Shear ◽  
Newtonian Constant ◽  
Video Fluoroscopy

AbstractThe Ultrasound Velocity Profiling (UVP) technique allows real-time, non-invasive flow mapping of a fluid along a 1D-measuring line. This study explores the possibility of using the UVP technique and X-ray video-fluoroscopy (XVF) to elucidate the deglutition process with the focus on bolus rheology. By positioning the UVP probe so that the pulsed ultrasonic beam passes behind the air-filled trachea, the bolus flow in the pharynx can be measured. Healthy subjects in a clinical study swallowed fluids with different rheological properties: Newtonian (constant shear viscosity and non-elastic); Boger (constant shear viscosity and elastic); and shear thinning (shear rate-dependent shear viscosity and elastic). The results from both the UVP and XVF reveal higher velocities for the shear thinning fluid, followed by the Boger and the Newtonian fluids, demonstrating that the UVP method has equivalent sensitivities for detecting the velocities of fluids with different rheological properties. The velocity of the contraction wave that clears the pharynx was measured in the UVP and found to be independent of bolus rheology. The results show that UVP not only assesses accurately the fluid velocity in a bolus flow, but it can also monitor the structural changes that take place in response to a bolus flow, with the added advantage of being a completely non-invasive technique that does not require the introduction of contrast media.

Sign in / Sign up

Export Citation Format

Share Document