Assessment of aeroelastic coupling between a shock boundary layer interaction and a flexible panel

The fluid-structural coupling between an impinging Mach 4 shock boundary layer interaction (SBLI) and a flexible panel is investigated using wall-resolved implicit large-eddy simulation (ILES). Since the prediction of fluctuating wall pressure remains a challenge in aeroelastic configurations with large flow separation regions, an exposition of the coupling processes associated with the difference in the wall pressure fields between the coupled and uncoupled interaction is sought. The distinction between the time-mean pressure, induced coherent fluctuations, and inherent pressure fluctuations is formalized using a triple decomposition. Further, the role of the time-mean aeroelastic condition is considered to delineate predominantly static and dynamic coupling mechanisms between the fluid and structure. This is achieved by computing the fluid solution over the time-mean panel deformation of the coupled interaction. The impinging shock induces a large, highly unsteady separation region, the mean and fluctuating quantities of which are augmented by the imposed aeroelastic state. The use of the time-mean aeroelastic condition as a static structural deformation in a fluid-only simulation is found to capture the mean wall pressure of the coupled condition and some, but not all, of the increased flow unsteadiness. A local piston theory model is then implemented over a portion of the panel to assess the degree of flow unsteadiness associated with classical quasi-steady fluid-structural coupling between the supersonic ensemble-mean flow and the structural dynamics. It is found that, after the flow reattachment point, the coherent, dynamically induced pressure can be linearly superimposed with the statically coupled pressure field to predict the coupled wall pressure fluctuations to a reasonable degree.