Lattice Boltzmann simulations of vortex entrapment of particles in a microchannel with curved or flat edges

Numerical simulations were conducted to determine the effects of flat-edge and curved-edge channel wall obstacles on the vortex entrapment of uniform-size particles in a microchannel with a T-shape divergent flow zone at different flow Reynolds numbers (Re). Two-particle simulations with a non-pulsating flow indicated that although particles were consistently entrapped in a vortex zone in a microchannel with flat-edge wall obstacles at all Re studied, vortex zone entrapment of particles occurred only at the lowest Re in a microchannel with curved-edge wall obstacles. In a microchannel with flat-edge obstacles, small particles avoided entrapment in vortices in a non-pulsating flow where large particles got trapped. Interparticle and particle-wall repulsive interaction potentials prevented vortex entrapment of particles in a microchannel with flat-edge wall obstacles only at high flow Re, revealing the existence of a threshold inertial force for particle liberation, if combined inertial and repulsive forces are considered in non-pulsating flow simulations. Pulsating flow enhanced the chance for liberation of particles that were otherwise trapped in vortices, but did not always ensure the particle liberation. Simulations with larger particle concentrations demonstrated that the location of particle-trapping vortices varied with changes in particle concentration. Simulation results further demonstrated the significance of particle retaining capabilities of vortices in a T-shape divergent zone within a microchannel.