Study on Aerothermal Effects of Viscous Shock Interaction in Hypersonic Inlets

The objective of this study is to gain insight into the complex flow phenomena, governing the aerodynamics of intakes for airbreathing space vehicles. Complementary to CFD-simulations, reliable wind tunnel experiments remain necessary for validation as well as for understanding physical effects and their impact on the overall design. The hypersonic blow down tunnel H2K with its long test duration ensures a fully established flow field to simulate external and internal compression processes of different inlet models with three ramps. The dominating flow phenomena of the inlet flow are viscous interactions of oblique shocks induced by the compression ramps with the boundary layers developing on the wall surfaces. An increase of the ramp angles lead to higher degree of pressure recovery, but is also linked to larger heat loads. Within this study, comprehensive information about thermal wall loads is gained by IR-thermography, i.e. thermal mapping of the PTFE model surfaces. In order to provide accurate heat transfer measurements, model temperature increase and radiation effects are taken into account by an instationary numerical data reduction algorithm. Complementary information about the inlet flow is obtained by flow visualizations and detailed pressure measurements. The influence of model parts like side walls or cowl are demonstrated and separation regions are determined with respect to the boundary layer state. The experimental results show a strong influence of the boundary layer on the flow field at the compression ramps. At the highest examined Reynolds number and with applied boundary layer tripping, the formation of the separation bubble was found to be sensitive on changes of the flow or the model conditions. Altogether, the experimental results on the hypersonic inlet flow provided a substantial insight into the aerodynamics of hypersonic propulsion components to support the design of future hypersonic space vehicles