Numerical simulations were carried out to examine the flow of dry granular materials around obstacles. Two numerical approaches were used. The first is a single-phase formulation based on a Particle-In-Cell (PIC) approach, and employs simplified expressions for the granular stresses. The second approach is based on a two-phase Eulerian-Eulerian formulation, and includes equations for the dynamic granular stresses based on the kinetic theory of granular materials. The code FLUENT 6.1 was used in that case.
The simulations of single-phase granular flow examined the patterns of flow around a flat plate, and the role of velocity, solids volume fraction and material properties. The results show that a granular shock wave develops in front of the obstacle, where velocities and solids volume fraction underwent a jump. A stagnant wedge inside the shock immediately in front of the obstacle was obtained. The predicted shapes of the granular shock agree with available descriptions of experimental observations. It was possible to use the two-phase model in those calculations by neglecting the interaction force between the two phases. The results were in agreement with those of the single-phase PIC model. The two-phase model was then used to examine the role of the interstitial gas. The results show that the presence of the gas phase can appreciably alter flow patterns, even for relatively coarse particles.