Crater formation in a cohesive granular bed by an impinging turbulent jet*

The erosion of particles by an impinging turbulent jet is observed in various situations, such as the cleaning of a surface or during the landing of a spacecraft. Beyond the threshold of erosion, a round turbulent jet of gas normally impinging a cohesionless granular bed displays an axisymmetric crater. Here, we experimentally consider the effects of inter-particle cohesion on the craters formed beyond the erosion threshold by controlling the cohesion between the grains and the momentum of the turbulent jet. We report the morphology of the steady-state craters observed. Our experiments show that the presence of cohesion significantly alters the erosion dynamics and, as a result, the craters that form. The morphology of the craters are described by extending the framework previously developed to describe the effects of cohesion on the onset of erosion in this geometry.