Particle volume fraction effects in simulations of turbulent channel flows

Direct numerical simulation and a Lagrangian particle tracking routine are used to simulate multiphase particle-laden flows through a channel at a shear Reynolds number of 300. The overall model is used to simulate 300k solid particles with a diameter of 100 µm at different levels of coupling between the particles and the flow field. In an attempt to reduce computational cost, a stochastic inter-particle collision model is implemented, which produces promising results. However, when the particle size, and hence volume fraction, is increased to 200 µm the predicted particle normal stresses no longer agree with results based on a fully deterministic collision approach.

To resolve this a second stochastic method is implemented based on a direct simulation Monte Carlo approach which generates probable collision events from pairs of nearby particles. The predictions based on this method are found to be satisfactory for both sizes of particle, and to be in good agreement with results based on the fully deterministic approach.