Effect of Plume Conditions and Granular Bed Properties on the Temporal Transitions in Mechanisms Driving Plume-Surface Interactions

Crater formation and evolution is a known consequence of Plume-Surface Interactions (PSI) that is associated with several adverse effects. The evolution of these craters is a dynamic process that is dictated by the characteristics of the plume and the physical properties of the granular surface. Depending on the operating conditions, the evolution of craters can be dictated by the presence of mechanisms such as bearing capacity failure, viscous erosion, and several others. The erosion process can be solely influenced by a single predominant mechanism or a combination of several of them over the time span of the interaction. Owing to the dynamic nature of PSI, transitions may occur from one mechanism to another. These transitions can manifest in the form of distinct crater profiles that are parabolic, annular, deep (steep-walled and cylindrical), or a composite of multiple shapes. This study aims to investigate the susceptibility of these temporal transitions by examining the crater profile transitions due to the effect of plume operating conditions and granular bed properties. This was performed by examining the transition time scales and crater growth properties extracted from NASA's Physics Focused Ground Test (PFGT1) crater data. Results highlighted the implications each of the operating conditions and granular bed properties has on the temporal transitions in crater geometry, and provided information regarding the mechanisms governing the crater evolution across the transition period.