High-resolution simulation of gas–solid suspension using macro-scale particle methods

Dynamic multi-scale structures in a gas–solid suspension with 1024 particles are investigated with direct numerical simulations using macro-scale particle methods. The suspension is found to be characterized by heterogeneity with clustering solids and bypassing gas. The solid particle velocity distribution is found to be anisotropic though nearly Maxwellian in each direction, which is in agreement with measurements in liquid–solid systems, supporting the necessity of incorporating anisotropy into the continuum descriptions of such flows. The drag force on the particles in the dilute phase can be far larger than that in the center of the dense phase, and much less than that on the phase interface, suggesting the insufficiency of correlating interphase friction to local averaged voidage only. However, statistics shows nearly Gaussian distribution of the drag forces, which is potentially favorable to establishing a diffusion model accounting for drag dispersion. The need for a multi-scale description of gas–solid flows, and on the other hand, the power of particle methods as exploring tools for this purpose, are demonstrated.