Sedimentation of colloidal particles near a wall: Stokesian dynamics simulations

1999 ◽  
Vol 1 (9) ◽  
pp. 2131-2139 ◽  
Author(s):  
Robert B. Jones ◽  
Ramzi Kutteh
Keyword(s):  
Colloidal Particles ◽  
Stokesian Dynamics ◽  
Dynamics Simulations

scholarly journals Short-time diffusion of charge-stabilized colloidal particles: generic features

2010 ◽  
Vol 43 (5) ◽  
pp. 970-980 ◽  
Author(s):  
Marco Heinen ◽  
Peter Holmqvist ◽  
Adolfo J. Banchio ◽  
Gerhard Nägele
Keyword(s):  
Experimental Data ◽  
Colloidal Particles ◽  
Stokesian Dynamics ◽  
Self Diffusion ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Dynamics Simulations ◽  
Short Time ◽  
Hydrodynamic Function

Analytical theory and Stokesian dynamics simulations are used in conjunction with dynamic light scattering to investigate the role of hydrodynamic interactions in short-time diffusion in suspensions of charge-stabilized colloidal particles. The particles are modeled as solvent-impermeable charged spheres, repelling each otherviaa screened Coulomb potential. Numerical results for self-diffusion and sedimentation coefficients, as well as hydrodynamic and short-time diffusion functions, are compared with experimental data for a wide range of volume fractions. The theoretical predictions for the generic behavior of short-time properties obtained from this model are shown to be in full accord with experimental data. In addition, the effects of microion kinetics, nonzero particle porosity and residual attractive forces on the form of the hydrodynamic function are estimated. This serves to rule out possible causes for the strikingly small hydrodynamic function values determined in certain synchrotron radiation experiments.

Normal stresses and microstructure in bounded sheared suspensions via Stokesian Dynamics simulations

2000 ◽  
Vol 412 ◽  
pp. 279-301 ◽  
Author(s):  
ANUGRAH SINGH ◽  
PRABHU R. NOTT
Keyword(s):  
Normal Stress ◽  
Couette Flow ◽  
Normal Stress Difference ◽  
Stress Difference ◽  
Normal Stresses ◽  
Plane Couette Flow ◽  
Stokesian Dynamics ◽  
First Normal Stress Difference ◽  
Particle Pressure ◽  
Dynamics Simulations

We report the normal stresses in a non-Brownian suspension in plane Couette flow determined from Stokesian Dynamics simulations. The presence of normal stresses that are linear in the shear rate in a viscometric flow indicates a non-Newtonian character of the suspension, which is otherwise Newtonian. While in itself of interest, this phenomenon is also important because it is believed that normal stresses determine the migration of particles in flows with inhomogeneous shear fields. We simulate plane Couette flow by placing a layer of clear fluid adjacent to one wall in the master cell, which is then replicated periodically. From a combination of the traceless hydrodynamic stresslet on the suspended particles, the stresslet due to (non-hydrodynamic) inter-particle forces, and the total normal force on the walls, we determine the hydrodynamic and inter-particle force contributions to the isotropic ‘particle pressure’ and the first normal stress difference. We determine the stresses for a range of the particle concentration and the Couette gap. The particle pressure and the first normal stress difference exhibit a monotonic increase with the mean particle volume fraction ϕ. The ratio of normal to shear stresses on the walls also increases with ϕ, substantiating the result of Nott & Brady (1994) that this condition is required for stability to concentration fluctuations. We also study the microstructure by extracting the pair distribution function from our simulations; our results are in agreement with previous studies showing anisotropy in the pair distribution, which is the cause of normal stresses.

scholarly journals Shear-induced particle diffusivities from numerical simulations

2001 ◽  
Vol 443 ◽  
pp. 101-128 ◽  
Author(s):  
MARCO MARCHIORO ◽  
ANDREAS ACRIVOS
Keyword(s):  
Ensemble Averaging ◽  
Stokesian Dynamics ◽  
System Of Particles ◽  
Novel Method ◽  
The Mean ◽  
Dynamics Simulations ◽  
Neutrally Buoyant ◽  
Solid Spheres ◽  
Good Agreement ◽  
Number Of Particles

Using Stokesian dynamics simulations, we examine the flow of a monodisperse, neutrally buoyant, homogeneous suspension of non-Brownian solid spheres in simple shear, starting from a large number of independent hard-sphere distributions and ensemble averaging the results. We construct a novel method for computing the gradient diffusivity via simulations on a homogeneous suspension and, although our results are only approximate due to the small number of particles used in the simulations, we present here the first values of this important parameter, both along and normal to the plane of shear, to be obtained directly either experimentally or numerically. We show furthermore that, although the system of equations describing the particle motions is deterministic, the particle displacements in the two directions normal to the bulk flow have Gaussian distributions with zero mean and a variance which eventually grows linearly in time thereby establishing that the system of particles is diffusive. For particle concentrations up to 45%, we compute the corresponding tracer diffusivities both from the slope of the mean-square particle displacement and by integrating the corresponding velocity autocorrelations and find good agreement between the two sets of results.

Directional locking and deterministic separation in periodic arrays

2009 ◽  
Vol 627 ◽  
pp. 379-401 ◽  
Author(s):  
JOELLE FRECHETTE ◽  
GERMAN DRAZER
Keyword(s):  
External Force ◽  
Hydrodynamic Interactions ◽  
Square Lattice ◽  
Stokesian Dynamics ◽  
Particle Mobility ◽  
Periodic Arrays ◽  
Moving Particle ◽  
Dynamics Simulations ◽  
Solid Obstacles ◽  
Vector Separation

We investigate the dynamics of a non-Brownian sphere suspended in a quiescent fluid and moving through a periodic array of solid obstacles under the action of a constant external force by means of Stokesian dynamics simulations. We show that in the presence of non-hydrodynamic, short-range interactions between the solid obstacles and the suspended sphere, the moving particle becomes locked into periodic trajectories with an average orientation that coincides with one of the lattice directions and is, in general, different from the direction of the driving force. The locking angle depends on the details of the non-hydrodynamic interactions and could lead to vector separation of different species for certain orientations of the external force. We explicitly show the presence of separation for a mixture of suspended particles with different roughness, moving through a square lattice of spherical obstacles. We also present a dilute model based on the two-particle mobility and resistance functions for the collision between spheres of different sizes. This simple model predicts the separation of particles of different size and also suggests that microdevices that maximize the differences in interaction area between the different particles and the solid obstacles would be more sensitive for size separation based on non-hydrodynamic interactions.

Stokesian Dynamics Simulations of Ferromagnetic Colloidal Dispersions in a Simple Shear Flow

1998 ◽  
Vol 203 (2) ◽  
pp. 233-248 ◽  
Author(s):  
Akira Satoh ◽  
Roy W. Chantrell ◽  
Geoff N. Coverdale ◽  
Shin-ichi Kamiyama
Keyword(s):  
Shear Flow ◽  
Simple Shear ◽  
Colloidal Dispersions ◽  
Simple Shear Flow ◽  
Stokesian Dynamics ◽  
Dynamics Simulations

scholarly journals Stokesian dynamics simulations of a magnetotactic bacterium

2021 ◽  
Vol 44 (3) ◽  
Author(s):  
Sarah Mohammadinejad ◽  
Damien Faivre ◽  
Stefan Klumpp
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Cell Body ◽  
Magnetic Moment ◽  
Magnetotactic Bacteria ◽  
Swimming Velocity ◽  
Stokesian Dynamics ◽  
Inclination Angles ◽  
Dynamics Simulations ◽  
The Magnetic Field

AbstractThe swimming of bacteria provides insight into propulsion and steering under the conditions of low-Reynolds number hydrodynamics. Here we address the magnetically steered swimming of magnetotactic bacteria. We use Stokesian dynamics simulations to study the swimming of single-flagellated magnetotactic bacteria (MTB) in an external magnetic field. Our model MTB consists of a spherical cell body equipped with a magnetic dipole moment and a helical flagellum rotated by a rotary motor. The elasticity of the flagellum as well as magnetic and hydrodynamic interactions is taken into account in this model. We characterized how the swimming velocity is dependent on parameters of the model. We then studied the U-turn motion after a field reversal and found two regimes for weak and strong fields and, correspondingly, two characteristic time scales. In the two regimes, the U-turn time is dominated by the turning of the cell body and its magnetic moment or the turning of the flagellum, respectively. In the regime for weak fields, where turning is dominated by the magnetic relaxation, the U-turn time is approximately in agreement with a theoretical model based on torque balance. In the strong-field regime, strong deformations of the flagellum are observed. We further simulated the swimming of a bacterium with a magnetic moment that is inclined relative to the flagellar axis. This scenario leads to intriguing double helical trajectories that we characterize as functions of the magnetic moment inclination and the magnetic field. For small inclination angles ($$\lesssim {20^{\circ }}$$≲20∘) and typical field strengths, the inclination of the magnetic moment has only a minor effect on the swimming of MTB in an external magnetic field. Large inclination angles result in a strong reduction in the velocity in direction of the magnetic field, consistent with recent observations that bacteria with large inclination angles use a different propulsion mechanism.Graphic abstract

scholarly journals Accelerated Stokesian Dynamics simulations

2001 ◽  
Vol 448 ◽  
pp. 115-146 ◽  
Author(s):  
ASIMINA SIEROU ◽  
JOHN F. BRADY
Keyword(s):  
Reynolds Number ◽  
Freezing Point ◽  
Computational Cost ◽  
Spherical Shape ◽  
Stokesian Dynamics ◽  
Reynolds Number Flow ◽  
Wave Space ◽  
Number Flow ◽  
The Many ◽  
Dynamics Simulations

A new implementation of the conventional Stokesian Dynamics (SD) algorithm, called accelerated Stokesian Dynamics (ASD), is presented. The equations governing the motion of N particles suspended in a viscous fluid at low particle Reynolds number are solved accurately and efficiently, including all hydrodynamic interactions, but with a significantly lower computational cost of O(N ln N). The main differences from the conventional SD method lie in the calculation of the many-body long-range interactions, where the Ewald-summed wave-space contribution is calculated as a Fourier transform sum and in the iterative inversion of the now sparse resistance matrix. The new method is applied to problems in the rheology of both structured and random suspensions, and accurate results are obtained with much larger numbers of particles. With access to larger N, the high-frequency dynamic viscosities and short-time self-diffusivities of random suspensions for volume fractions above the freezing point are now studied. The ASD method opens up an entire new class of suspension problems that can be investigated, including particles of non-spherical shape and a distribution of sizes, and the method can readily be extended to other low-Reynolds-number-flow problems.

Shear thinning of suspensions of sterically stabilized spheres studied by Stokesian dynamics simulations

2000 ◽  
Vol 113 (6) ◽  
pp. 2484-2488 ◽  
Author(s):  
H. M. Schaink ◽  
P. A. Nommensen ◽  
R. J. J. Jongschaap ◽  
J. Mellema
Keyword(s):  
Shear Thinning ◽  
Stokesian Dynamics ◽  
Dynamics Simulations
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