Unsteady Surface Pressure Fluctuations Due to Surface Deformations on an Airfoil in a Uniform Mach 6 Flow

Hypersonic vehicle control fins experience pressure and thermal loads which cause steady and unsteady surface deformations. The aerodynamic response to the unsteady deformations must be characterized and are often approximated by local piston theory, which bases the pressure response on a local inviscid steady state. However, this methodology does not incorporate the effects of viscosity, mostly through the presence of a boundary layer, as well as the influence of flow complexities, such as multiple adjacent deforming surfaces. In this work, deformation of single and tandem surfaces on a representative airfoil geometry in a Mach 6 freestream is forced based on linear beam theory, with a range of beam modes considered. The unsteady aerodynamic response predicted by local piston theory, two-dimensional versions of boundary element theory, Euler-based CFD, and Navier-Stokes-based CFD at different Reynolds numbers are compared and discussed.