The particle erosion and diffusion behaviours due to an air-jet impingement on a granular bed covering a simplified terrain model

Abstract

A perpendicular jet impingement on a granular bed covering uneven terrain causes complex particle erosion and diffusion behaviours. Such a situation is most likely to occur at a plume-regolith interaction in planetary exploration missions. A plume due to a retrorocket impinges on regolith over a planetary surface in a soft-landing sequence. In this study, we focus on the understanding of basic terrain effects and investigate numerically a subsonic jet impingement on the granular bed covering a rectangular hump using a two-way coupled fluid-particle interaction method. Moreover, the experiments are conducted to determine the suitable numerical parameters: turbulence parameters, friction coefficient of particles, and coefficient of restitution. Both particle erosion and diffusion behaviours are numerically investigated at several hump positions and heights, and consequently the hump position strongly influence the particle diffusion and erosion behaviours. Erosion due to the bearing capacity failure continues to occur from the initial elapsed time in the case of the jet impingement around the hump close to a jet axis. This is because the gas interaction with the hump leads to the velocity reduction of a diffusion gas velocity, and it is lower than a particle velocity in most of the regions. Additionally, the deposited particles in a cavity formed by the close hump are difficult to be diffused because the particles stagnate by the downward impinging jet flow.