Fluid/Structure Interaction of Cantilevered Plate in Supersonic Separated Flow

The fluid-structure interaction of a cantilevered plate geometry in Mach 2 flow was studied experimentally to assess the effects of structural compliance on the surrounding flowfield. The test geometry, representative of a compliant control surface, consists of an overhanging plate that extends past the edge of a backward-facing step to create a separated region in the flow. This allowed for the study of recirculation effects and unsteady pressure forcing on the cantilevered plate without shock/boundary-layer interactions that would be present if the plate were inclined to the flow. Rigid and compliant test articles were studied to capture the fluid response with and without structural deformation. Schlieren photography and particle image velocimetry showed that under the unsteady conditions during startup of the wind tunnel the flexible plate exhibited a highly dynamic oscillatory response with frequencies similar to its natural vibration response. Under steady, started supersonic flow conditions, the flexible cantilever exhibited smaller oscillations around a mean deflection of two plate thicknesses. Oil flow visualization revealed nontrivial three-dimensionality of the test section flowfield. Modal decomposition of stereo digital image correlation measurements demonstrated that the distinct frequencies present in the flexible plate’s response consistently correspond to the same mode shapes.