Sedimentation of an elliptic rigid particle in a yield-stress fluid: A Lattice-Boltzmann simulation

Abstract

Sedimentation of a single, two-dimensional, rigid, elliptic particle in a biviscous fluid contained in a finite, closed-ended channel is studied in this work using the lattice-Boltzmann method. The main objective of the work is to numerically investigate the role played by a fluid’s yield stress on the trajectory, orientation, and terminal velocity of such a particle for different density and aspect ratios. Numerical results suggest that a new mode of settling might emerge for yield-stress fluids, which is nonexistent for Newtonian fluids. That is, a particle released from the rest state at the midplane with a prescribed, nonzero, inclination angle (with respect to the horizontal line) migrates toward the left side-wall (if the inclination angle is positive) soon after it is released but changes course after a short while and moves back toward the centerline where the voyage started. However, while for Newtonian fluids the particle eventually returns to the centerline and continues its free fall with a horizontal orientation, for yield-stress fluids, the particle might finally lodge at a specific distance away from the centerline and continue its fall assuming a nonhorizontal orientation. The offset position is predicted to be a function of the Bingham number and the density ratio but independent of the initial inclination angle.

Jeffery orbits in shear-thinning fluids

“…In this proceeding, the authors show a slight reduction in angular velocity that diminishes with particle aspect ratio. Sobhani et al [46] also studied the dynamics of an elliptic particle in a yield-stress fluid using the lattice-Boltzmann method. In this paper we consider the dynamics of a neutrally buoyant three-dimensional prolate spheroid in a shear flow of a weakly shear-thinning fluid.…”

Numerical Analysis of Non-Newtonian Fluid Effects on the Equilibrium Position of a Suspended Particle and Relative Viscosity in Two-Dimensional Flow

“…In this study, we used the Herschel-Bulkley model as a model that can express a non-Newtonian solvent [13,24]. This model can change solvent properties by changing the power-law index n and Bingham number Bn.…”

“…As mentioned above, many studies have used a Newtonian fluid as a solvent, and power-law fluid has often been used in the studies about non-Newtonian fluid. On the other hand, in a study using a solvent that had yield stress in a channel flow, Sobhani et al [13] suggested that the equilibrium position of the rigid elliptical particle in Bingham fluid was different from that in Newtonian fluid when the particle with gravity settled. Furthermore, Chaparian et al [14] reported that Bingham fluid affected the equilibrium position when elastoviscoplastic fluid was used.…”

Simulation of bidisperse colloidal centrifugal sedimentation using a mixture viscosity model

“…There are also other complex simulations using approaches such as the Masliyah-Lockett-Bassoon (MLB) model, 19,27 force coupling method (FCM), 28 effective-medium model, 29 or effective voidage model 30 to predict the settling velocities of two interfaces, which require significant computation time. Furthermore, the settling of different shaped particles, in particular ellipses, 31,32 has been simulated to establish the dynamics of systems with wider application. Other nonspherical particles such as rods 33,34 are also drawing attention in recent years and are more oriented toward industrial applications such as pharmaceuticals.…”