Flow over and inside Mars-like impact craters: an experimental study

The morphological processes that control the evolution of impact craters are yet to be fully understood. Recent studies have hypothesized a specific mechanism based upon long-term aeolian deflation of the original intracrater sediment deposit. In this work we perform physical modeling of Martian craters, including idealized craters based used in previous work. This study used a refractive index matching (RIM) approach. Transparent models of craters were fabricated by casting acrylic resin material into 3D printed molds. PIV velocity measurements were performed to reveal the instantaneous 3D flow structures generated by the crater ridge and mound, as well as to observe their evolution. The flow scenario revealed by our measurements is consistent with previous numerical work and supports the exhumation hypothesis previously proposed. Two streamwise oriented high-stress regions suggest that the wake is populated by counter-rotating eddies which are shed by the mound, convect downstream and eventually impinge onto the rim. 3D measurements reveal the shedding of complex alternating counter-rotating vortices caused by the mound.