Effects of flexible panels on normal shock trains and performance of scramjet isolators

The understandings of shock trains in isolators are crucial to the development of scramjets. However, recent studies have mainly focused on the flow structures in rigid isolators. The potential fluid-structure interactions between flexible structures and the extreme internal flow conditions receive a little attention. The current study intends to fill this gap by two numerical campaigns where the impacts of elastic panels and boundary layer thickness are investigated. The impacts of fluid-structure interactions are quantified by 11 flow parameters regarding structural response, separation zone, shock structure, flow asymmetry and performance. Analyses show that the fluid-structure interactions lead to the limit cycle oscillation of panel with almost the same structural responses for all cases. For isolators with an elastic panel at the bottom wall, the separation zones and shock trains significantly travel upstream with increasing length and violent transient fluctuation. The flow becomes more asymmetric with large transient side loads. The performance is seriously compromised by the decrease in average performance and large-amplitude fluctuations. For isolators with an elastic panel at both walls, the separation zones and shock train further travel upstream, the flow becomes symmetric without transient side loads, and the performance further decreases because of more drastic transient fluctuation. Moreover, the boundary layer thickness has a great influence on fluid-structure interactions in the isolator. With increasing boundary layer thickness, separation zones and shock trains significantly travel upstream, the transient side loads decrease, and the average performance improves.