Predicting Fracture of Atmospheric Ice in Hypersonic Shock Layers

Ice clouds permeate the atmosphere of Earth at widely varying altitudes, posing a risk of impact and erosion to hypersonic vehicles. Before vehicle impact, atmospheric ice must traverse a shock layer, encountering aerodynamic loads, drag forces, and heat transfer. These interactions can affect both the location and energy of the particle impact. The pre-impact interaction of ice particles with the high-pressure shock layer in front of the vehicle is considered in this work. A two-way coupled fluid-structure interaction framework is utilized to investigate the interaction of an ice agglomerate with the normal part of a bow shock produced by a vehicle traveling at Mach 3. The fluid-structure interaction framework is a partitioned system, where the flow is simulated by the direct simulation Monte Carlo technique, and structures are simulated by the lattice particle method. These two simulation domains are coupled through the marching windows method, a surface interfacing technique based on the marching cubes procedure. A loose coupling scheme is applied to simulate the structural interaction of the normal shock wave with the ice structure at a high altitude. The effect of ice material strength on the likelihood of aerodynamically induced agglomerate separation is studied. It is found that ice particles with strengths on the order of the dynamic pressure experienced by the ice particle undergo agglomerate break-up and possibly catastrophic damage in individual ice geometries. Material strength one order of magnitude larger than dynamic pressure is sufficient to prevent substantial damage in the constituent geometries of the agglomerate, but not to prevent damage in the connection region.