Numerical Study of Heat Flux Reduction Mechanism of the Counterflowing Jet in Rarefied Flows

Aerodynamic heating in hypersonic flow presents one of the most serious challenges in the design of space vehicles. In the present study, heat flux reduction mechanism of the pulsed counterflowing jet from the nose of a blunt body is numerically investigated. Flow field around the hemisphere model is calculated in hypersonic free stream of Mach number 10 and Knudsen number 0.4. Considering that the external flow field is highly rarefied, recent works have demonstrated the direct simulation Monte Carlo (DSMC) technique to accurately predict the flow field under steady-state conditions. For supersonic flow with a counterflowing jet, the mean free path could vary by orders of magnitude within the computation domain and the computational mesh size in DSMC should be of one third of local mean free path (MFP) of the gas due to the requirement of selecting colliding partners among particles. Therefore, the open-source SPARTA code with octree Cartesian mesh is utilized in our research with Adaptive Mesh Refinement (AMR), which has been widely used in modern DSMC codes. AMR is crucial for efficient solutions of multi-scale problems characterized by large gradients of parameters in localized areas of the computational domain. Currently, tree-based methods have being developed for extremely large scale AMR simulations with billions of cells. As a conclusion, significant decreases of surface heat flux are obtained and counterflowing jet is proved to be effective on heat flux reduction in the vicinity of the stagnation point.