A Fluid-Structure Computational Framework for Atmospheric Ice in Hypersonic Environments

Ice particles on the order of one to several hundred micrometers suspended within clouds in the atmosphere present a danger to hypersonic vehicles. The fluid-structure interactions (FSI) of these particles with the post-shock environments generated by hypersonic vehicles are not well understood, and the state of the particle at the time of vehicle impact is unknown. Dynamic, brittle fracture of the ice is possible in these conditions, and the interactions occur at small length scales and short time scales. Current FSI simulation capabilities are inadequate to capture the noncontinuum and dynamic fracture effects. A novel, two-way coupled fluid-structure interaction framework for two-dimensional systems is presented which uses direct simulation Monte Carlo (DSMC) and the lattice particle method (LPM) to investigate this problem. These two techniques make this framework very suitable for hypersonic flows at high altitudes and at small characteristic lengths, the conditions of flows around atmospheric ice. DSMC, when compared to standard computational fluid dynamics methods, can more effectively capture noncontinuum effects. The discretization and simulation techniques used by LPM allow this framework to easily simulate mechanical failure and crack propagation throughout a solid. The LPM subsystem is also capable of modeling solids of varying composition, using averaging to calculate interface properties. This capability is also useful for studying ice agglomerates made from dissimilar primary particles. The coupling subsystem utilizes the marching squares algorithm to dynamically update both the geometry of boundaries in the fluid flow and the aerodynamic forces which are applied to the solid material points. Verification is performed on the system using simple test cases with analytical solutions, and validation is planned for future work. The framework presented here is to be used to study the effects of post-shock flows produced by hypersonic vehicles on atmospheric ice cloud particles for the purpose of aiding damage prediction for ice-vehicle collisions.