Thermal Non-equilibrium and Conjugate Heat Transfer Effects for Four Canonical Hypersonic Test Cases: Numerical Validation and Analysis

The extreme temperatures experienced by hypersonic vehicles during flight or atmospheric reentry, if not appropriately mitigated, can easily exceed the employed materials' allowable temperature limits and destroy the vehicle. Therefore, the accurate prediction of heat fluxes on the surfaces of a hypersonic vehicle is critical to a successful design. High-fidelity numerical simulations can provide valuable insights into the pressure forces and the heat flux magnitude, and their distribution on the vehicle’s surface; in addition, a conjugate heat-transfer CFD simulation can also provide the temperature distribution throughout the airframe structure. By necessity, numerical predictions capable of this level of accuracy need to include fundamental physical phenomena such as compressibility, turbulence, heat transfer, thermal and chemical non-equilibrium. Also, these numerical tools need to have a high level of proven accuracy and reliability to be fully trusted by the scientific and design community. This work presents the validation of a numerical approach used by the commercial CFD code Ansys Fluent to predict the heat fluxes on the surface of three canonical hypersonic test cases. The flow in these test cases includes complex physical phenomena such as thermal non-equilibrium, turbulence, and conjugate heat transfer. The study makes use of the density-based coupled solver available in the CFD code. Both the Roe flux-difference splitting and the AUSM+ flux-vector splitting formulation are used to calculate the convective fluxes. The solutions are converged to a steady state using an Incomplete Lower Upper factorization (ILU) in conjunction with coupled algebraic multigrid (AMG) method. For thermal non-equilibrium, the Park II model is used.