(170d) Numerical Simulations of Granular Materials Flow around Obstacles: the Role of the Interstitial Gas

A two-fluid model was used to determine the influence of the gas phase on granular flow interaction with obstacles. The governing equations of two-dimensional, two-phase flow were solved numerically using a Finite Volume based numerical code. The numerical results are compared qualitatively to experimental results from various sources, and good agreements are found. Several cases were tested in order to examine the role of the velocities of both phases, solids volume fraction, particle diameter, and gravity. Values of those variables were specified at the inlet boundary. The results show that, under certain conditions (particularly for dilute flows), a bow granular shock wave clearly forms in the front of the obstacle. Alternatively, for dense flows, granular shock waves were not observed. Based on the present observations, it appears that the formation and the shape of the bow granular shock wave are highly dependent on the presence of the interaction between the solid and gas phases. Therefore, it was concluded that the common assumption of neglecting the influence of the gas phase on the granular flow, may be appropriate only in the vicinity of the obstacle, where granular creeping flow takes place.