Surface Properties of Double-Fin Generated Shock-Wave/Boundary-Layer Interactions

What is it about?

Shock-Wave/Boundary-Layer Interaction (SBLI) is ubiquitous in high-speed air vehicles. In the present study, the surface flowfield properties for SBLI of crossing shocks induced by symmetric Double-Fins (DF) at fin angles of 8° and 10° at a freestream Mach number of 2 are experimentally investigated; a Single-Fin (SF) with 10° fin angle case is also explored as a comparison. Surface flow visualization is used to capture distinct flowfield structures such as separation and upstream influence. Steady and unsteady Pressure-Sensitive Paint (PSP) are used to obtain global surface pressure fields. In situ refinement of the PSP calibration using unsteady pressure sensors anchored the unsteady pressure distribution on the surface beneath the SBLI. The distinct characteristics of DF SBLI surface topology are discussed by comparing the corresponding SF configuration. Furthermore, the effect of fin angle on DF SBLI is characterized, and unsteady dynamics of the pressure field in the interaction region are examined through spectral techniques. Spectral Proper Orthogonal Decomposition (SPOD) analyses are performed on the unsteady PSP data, and the existence of traveling surface pressure waves and their frequency dependent behavior are discussed in detail. Dispersion relation of the surface pressure waves is revealed by performing 2-D space-time Fourier transform on the unsteady PSP data, and the results are compared with the phase velocity obtained from SPOD. Also, accompanying group velocity behavior is examined for distinct regions of the interaction wherein wave propagation is found dependent on its frequency. Steady surface pressures along the centerline are compared with previous experimental data. Fin-tip-spacing is found to be an essential parameter for scaling of upstream influence length, whereas Normal Mach number of the oblique shocks is used to determine the interaction strength of SBLI.

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