Erosion of cohesive grains by an impinging turbulent jet

The erosion and transport of particles by an impinging turbulent jet in air is observed in various situations, such as the cleaning of a surface or during the landing of a spacecraft. The presence of interparticle cohesive forces modifies the erosion threshold beyond which grains are transported. The cohesion also influences the resulting formation and shape of the crater. In this paper we characterize the role of the cohesive forces on the erosion of a flat granular bed by an impinging normal turbulent jet in air. We perform experiments using a cohesion-controlled granular material to finely tune the cohesion between particles while keeping the other properties constant. We investigate the effects of the cohesion on the erosion threshold and show that the results can be rationalized by a cohesive Shields number that accounts for the interparticle cohesion force. Despite the complex nature of a turbulent jet, we can provide a scaling law to correlate the jet erosion threshold, based on the outlet velocity at the nozzle, to a local cohesive Shields number. The presence of cohesion between the grains also modifies the shape of the resulting crater, the transport of grains, and the local erosion process.

Automated summary

This paper investigates the effect of interparticle cohesive forces on the erosion of a flat granular bed by an impinging turbulent jet in air. The experiments show that the cohesive forces influence the erosion threshold and can be explained by a cohesive Shields number. Additionally, the cohesive forces also affect the shape of the resulting crater, the transport of grains, and the local erosion process.