Multiscale Hypersonic Flow

 

Re-entry Vehicles

The design and utilization of space re-entry vehicles have been the subjects of interest by many aerospace engineers and entrepreneurs in recent years. The related technology resulted in SpaceX's success with the Falcon 9 reusable rocket in cutting down the costs of launches and moving a step closer to the commercialization of space travel.

One of the most fundamental challenges to the problem is the high aerothermodynamic load the vehicle is subject to during re-entry. Therefore, it is crucial to accurately analyze the non-equilibrium multiscale hypersonic flow around the vehicle during re-entry in designing the Thermal Protection System. However, the problem is that ground experiments replicating such an environment are costly and error-prone. Therefore, numerical analyses are handy in designing space re-entry vehicles. 

During the Entry, Descent, and Landing (EDL) sequence, a space re-entry vehicle experiences a wide range of flow regimes where Navier-Stokes equations assuming continuum may fail to be valid. For example, at high altitudes, the degree of rarefaction makes Computational Fluid Dynamics (CFD) analysis inadequate in giving accurate results. Furthermore, at lower altitudes where most flow regions are within the range where the Navier-Stokes equation is valid, some local regions, such as interiors of a shock and wall boundary layers, are characterized by strong thermal non-equilibrium. As such, multiscale hypersonic flow requires a particle-based approach for accurate simulations. 

Martin Alexandre, Iain D. Boyd, "Strongly coupled computation of material response and nonequilibrium flow for hypersonic ablation", Journal of Spacecraft and Rockets 52 (2009): 90-104