Inertial migration of circular particles in Poiseuille flow of a power-law fluid

Abstract

The immersed boundary-lattice Boltzmann method is used to study the inertial migration of particles in Poiseuille flow of a power-law fluid. The effects of Reynolds number, power-law index, and blockage ratio on the formation of particle trains are explored. The results show that single particle with different initial positions reach the same equilibrium position for the same power-law index. The stable equilibrium position moves closer to the centerline under the higher power-law index and blockage ratio. One-line of eight particles distributed initially at a vertical position will migrate laterally to the vicinity of the wall and form single-line particle trains. The particle spacing is unstable and increases when particles migrate to the equilibrium position. The inertial focusing length is an important factor for analyzing the formation of particle trains, which will be longer with increasing the power-law index. The mean particle spacing will be reduced with increasing Re and blockage ratio. Two-lines of 12 particles distributed initially and abreast along both sides of the centerline will migrate to the vicinity of the wall and form staggered particle trains. Due to the multiparticles interaction, the final particle equilibrium position will deviate from the single particle equilibrium position. The axial spacing between two neighboring particles is stable or fluctuates within a certain range. The particle spacing decreases with increasing the power-law index and blockage ratio, and with decreasing Re. The shear-thinning fluid is beneficial to the formation of single-line particle trains and staggered particle trains.