Spatially resolved mean and unsteady surface pressure in swept SBLI using PSP

Strong crossflow and swept separation are key aspects of the flow dynamics of 3-D shock wave/boundary layer interactions. This study explores the global surface pressure field beneath the canonical interaction produced by a sharp fin with deflection angle $$15^\circ$$ with a turbulent incoming boundary in a Mach 2 freestream flow. This corresponds to an interaction of moderate strength, and the unsteady pressure distribution captures pressure fluctuations associated with separation shock motion upstream of the interaction. Details of the PSP calibration are also described where the calibration process combines both a priori (with separately painted test coupon) and in situ calibration (with pressure tap measurements during test). Flow features are identified directly from the quantitative pressure distribution and compared to qualitative surface oil flow visualizations. The technique facilitates measurement of the pressure distribution on surfaces that have been difficult or impossible to instrument, such as the face of the shock-generating fin. The unsteady paint response is captured simultaneously with unsteady pressure transducers on the surface underneath the interaction, and a frequency response function based on this comparison is presented. As the results discussed herein demonstrate, the use of PSP allows one to capture significantly more information about this complex, highly three-dimensional interaction with details that are not easily obtained using traditional sensors, while also providing a more informed global view of the interaction. The utility and limitations of the technique in application to supersonic wind tunnel experiments are discussed.