Numerical simulation of hydrodynamic focusing of particles in straight channel flows with the immersed boundary-lattice Boltzmann method

摘要

Hydrodynamic focusing of particles instraight channel flows is studied by a hybrid immersed boundary (IB)-lattice Boltzmann (LB) method. In this method, the multi relaxation time (MRT)-LB equation with a force term is utilized to model the incompressible fluid flow over a regular Eulerian grid, and the IB method is employed to couple the finite element method based membrane model which represents the particle dynamics in fluid flow. The present method was validated by studying the three-dimensional top-lid-driven flow and the transient deformation of an initially spherical capsule under shear flow, and there were good agreements with previous theoretical and numerical results. Simulations of hydrodynamic dynamics in straight channels were performed to demonstrate the versatility of the hybrid method. The results show that Reynolds number and particle size are the important factors influencing focusing dynamics. The particles are focused onto their equilibrium positions at suitable Reynolds numbers of the channel flow. The higher the Reynolds number is, the more outward the equilibrium positions will be. The capability of the present method in studying the hydrodynamic separation of particles with different sizes and the transition of multi equilibrium positions were also discussed. This work also demonstrates the potential usefulness of IB-LBM in studying particle focusing, separation and sorting in confined flows.