Investigation of energy accommodation coefficient at gas-solid interface of a hypersonic flying vehicle

An effective thermal protection system is crucial for hypersonic flying vehicles performing multiple cycles of flight under high aerodynamic heating loads. Accurate calculation of heat transfer between a flying vehicle and its front shock waves is not possible due to complex gas-solid interactions. In this study, it was observed that the energy accommodation coefficient (EAC) at the interface between the shock wave formed by monoatomic gas and the flying vehicle exhibited a decrease-increase trend, which is attributed to that the averaged lasting time for each gas atom interacting with the solid decreases exponentially while the interacting depth increases logarithmically with the increase of the flight velocity. A one-dimensional collision model disclosed that the minimum EACs at different spring-mass systems occurred at the same Deborah number, indicating that the incident velocity of gas atoms corresponding to the minimum EAC is proportional to the natural frequency of the spring-mass system. Our research results suggest that the EAC strongly depends on the vehicle flying velocity and provide a rule for the optimal design of an efficient thermal protection system. (C) 2022 Elsevier Masson SAS. All rights reserved.