Conjugate Heat Transfer Simulations for Hypersonic Vehicles

Abstract

The accurate prediction of thermal responses is important for optimizing the design and operability for hypersonic flight vehicles. In order to efficiently simulate this process, a loosely coupled conjugate heat transfer solver was developed. Conjugate heat transfer simulations involve fluid and solid solvers. The fluid solver computes the flow field over the vehicle, and the solid solver calculates the transient heat conduction into the vehicle body. The two solvers are ``loosely'' coupled because both solvers exchange information at the surface of the vehicle, but operate on different time scales. The present work details the derivation of the conjugate heat transfer solver. The simulations were performed with US3D, an implicit finite volume unstructured compressible flow solver, with a newly developed implicit finite element transient heat conduction solver. The finite element solver is verified by comparing with analytical solutions for a bar, cylinder, and sphere. Validation cases for two geometries are shown: a fin-cone and HIFiRE-1. Both cases were shown to match well with the experimental data and flight test data. Additionally, the finite element method is compared to a finite volume method for solving the transient heat conduction equation. The comparison showed the benefits of the finite element method, such as refined temperature distribution and improved grid independence. Finally, the boundary layer transition (BoLT) vehicle is simulated for a segment of the trajectory. Results show the heating of the leading edge through time and the three-dimensional heating of the vehicle. At a specific time in the trajectory, the boundary layer and flow field are investigated. A comparative study is performed for the variable wall temperature and isothermal wall flow fields. The variable wall temperature was found to affect the wall heat flux and flow field structures. These results highlight the importance of performing conjugate heat transfer simulations when comparing to flight tests and experimental data.