Simultaneous planar piv and sdic measurements of an axisymmetric jet flowing across a compliant surface

The interaction of an underexpanded jet and a nearby adjacent compliant surface is considered in an effort to gain insight into the relevant fluid-structure interaction. High-quality simultaneous flowfield and surface-deflection data were obtained in this high-Reynolds number flow using non-intrusive, fullfield, optical diagnostics (planar particle image velocimetry and stereo/3D digital image correlation, respectively). Both experimental setups were rigorously validated in terms of their measurement resolution and accuracy, both individually, and in a combined manner. The fullfield surface deflection data indicate that the surface has a predominantly quasi-static response characterized by a ‘standing-wave’ type contour along the jet axis. A large jetward deflection, on the order of 10 plate thicknesses, was observed near the first shock cell region, which is consistent with previously obtained rigid-surface case surface pressure measurements. The compliant-surface flowfield was analyzed and compared to the rigid-surface case results in key regions: the initial expansion region, through the shock/boundary-layer interaction (SBLI), the SBLI separation region, the shock cell structure of the remainder of the jet plume, the near-wall boundary layer, and the farfield conditions. Notable differences were observed before, within, and after the SBLI region, as well as within the boundary layer, and in the shock-cell structure.