Jet-induced 2-D crater formation with horizontal symmetry breaking

TL;DR

This study examines how a gas jet creates and shapes a crater in granular material, revealing a logarithmic growth pattern and a symmetry-breaking phenomenon that could impact planetary lander safety.

Contribution

It provides new insights into the dynamics of crater formation and the conditions leading to horizontal symmetry breaking in granular beds under jet impingement.

Findings

Crater depth grows logarithmically over time.

Horizontal symmetry breaking occurs under specific conditions.

Asymmetric states have distinct evolution patterns.

Abstract

We investigate the formation of a crater in a 2-D bed of granular material by a jet of impinging gas, motivated by the problem of a retrograde rocket landing on a planetary surface. The crater is characterized in terms of depth and shape as it evolves, as well as by the horizontal position of the bottom of the crater. The crater tends to grow logarithmically in time, a result which is common in related experiments. We also observe a horizontal symmetry breaking at certain well-defined conditions which, as we will demonstrate, could be of considerable practical concern for lunar or planetary landers. We present data on the evolution of these asymmetric states and attempt to give insights into the mechanism behind the symmetry-breaking bifurcation.