Flowfield characteristics of a supersonic jet impinging on an inclined surface

The study of the flowfield and noise characteristics of supersonic impinging jets is important as these configurations can be found in many engineering applications, such as short takeoff and landing vehicles, hot surface cooling mechanisms, cold gas dynamic spray processes, and turbomachinery systems. This study experimentally investigates the flowfield characteristics of supersonic jets impinging on an inclined surface with nozzle-to-plate distances of 1.8D_j and 2.46D_j (D_j is the jet hydraulic diameter) and nozzle pressure ratios (NPRs) of 3.7 and 5.9. The two-dimensional two-component velocity fields were acquired in the central plane of the test nozzle and along the 45° inclined impingement surface by using a planar particle image velocimetry (PIV) technique. The flow characteristics of supersonic impinging jets, such as mean velocity and turbulent kinetic energy, were computed from the acquired PIV velocity vector fields, and the statistical profiles were compared to study the effects of the impingement surface and NPRs on the flow characteristics. The obtained statistical results have shown the presence of shock cells near the nozzle outlet, oblique plate shocks near the impingement, and tail shocks along the inclined surface. In addition, spatial two-point cross-correlations of turbulent velocity were computed using the PIV velocity vectors to study the sizes, shapes, and orientation of turbulent flow structures in the impinging jets. Finally, a proper orthogonal decomposition analysis was performed on the collections of velocity snapshots extracting the coherent flow structures of a supersonic jet impinging on an inclined surface.