Numerical analysis of rarefied hypersonic flows over inclined cavities

A comprehensive numerical analysis is conducted to investigate rarefied hypersonic flows over twodimensional (2-D) and three-dimensional (3-D) non-rectangular cavities with inclined front or rear walls using the direct simulation Monte Carlo (DSMC) method. The objective is to give a contribution to the understanding of the effects of inclined front or rear walls on flow features and aerodynamic surface quantities. The 3-D or finite-span effects are also analysed in depth. Results show that inclining the front wall of the cavity has a negligible effect on gas flows in the rear part of the cavity, and consequently does not affect surface pressures on and heat fluxes to both the cavity floor and the rear wall. This is because high-speed gases enter the cavity via the top of the rear wall, which is exactly the dominant drive force for gas flows in the rear portion of the cavity. Inclining the front wall does not alter this drive force, so it does not influence gas flows there. However, inclining the rear wall not only strongly influences the flows close to the rear wall, but also has a profound influence on the flows in the front portion of the cavity. Specifically, it can substantially enhance the flow expansion in the front portion of the cavity, make the front vortex shorter and moves the front vortex upward and leftward. The 3-D or finite-span effects play an important role in the flow features and surface quantities of rectangular, inclined-front, and inclined-rear cavities. The finite-span effects exhibit as the 3-D relieving effects, which prevent the external stream from penetrating deeper into the cavity. This consequently lessens the momentum and energy that are transferred into the cavity and brings about a significant decrease in the pressure on and heat flux to the cavity floor. The results in the work can be applied to the accurate prediction of the pressure and heating loads of the thermal-protection tiles of hypersonic vehicles. & COPY; 2023 Elsevier Ltd. All rights reserved.