A.O. Başkaya, M. Capriati, D. Ninni, F. Bonelli, G. Pascazio, A. Turchi, T. Magin, S. Hickel (2022)
AIAA Aviation Forum, Chicago. AIAA paper 2022-3276. doi: 10.2514/6.2022-3276

Verification and validation results of two immersed boundary solvers, INCA and CHESS, for atmospheric entry flows characterized by complex fluid thermochemistry and gas-surface interactions (GSI) are presented. Results are compared with those obtained with the body-conforming solver US3D, which is coupled to the same external thermochemistry library, Mutation++, as INCA and CHESS. In these campaigns, the INCA solver has shown an almost perfect agreement with the body-conforming reference solver and other reference results from literature.

A promising approach for the simulation of complex geometries is the use of immersed boundary methods (IBM) and adaptive mesh refinement techniques (AMR). These methods offer reliable and efficient mesh generation and adaptation with minimal user intervention; however, the accuracy of the numerical schemes used for predicting surface quantities must be analyzed rigorously. We find that exact conservation of mass, momentum, and energy, such as provided by the cut-element method in INCA, is an absolutely crucial basis. Conservation errors of other IBM algorithms can have a large effect in the presence of strong velocity, temperature and concentration gradients.

It is clear that simulating these complex flows still involves significant uncertainties regarding surface boundary conditions. We remark that the selection of a set of well defined test cases by mutual collaboration between research groups is crucial in converging to a scientific consensus on the prediction of these surface states. To that end, this paper establishes such a set of fundamental verification and validation cases to assess the performance of solvers and models for reacting surfaces under conditions relevant for atmospheric entry.