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This work investigates surface pressure unsteadiness on a compliant panel under a shockwave/boundary-layer interaction (SBLI) induced by a 2D compression ramp with an angle of 20o in a Mach 2 wind tunnel. High-speed digital image correlation (DIC) and fast-response pressure-sensitive paint (PSP) measurements are used to measure the panel displacement and panel and ramp-face surface pressure fluctuations at 5kHz and 20kHz, respectively. The data reduction technique of POD (proper orthogonal decomposition) was employed both for pressure and displacement fields. POD mode distribution for the pressure fields reveals that the first six modes have 60% of the total energy and exhibit low-frequency content for both rigid and compliant panels. The vibration of the compliant panel was seen to alter the energy distribution of the high energy modes as compared to the rigid panel case. The cross-correlations between the displacement and pressure modes were made using the time coefficients. This analysis shows significant correlations were present among the lower modes. The highest correlation was between displacement mode 1 and the pressure mode 4, which stemmed from the upstream of the intermittent region. The analysis was also made for the surrogate shock foot and reattachment lines. The correlation shows that panel vibration lowersmore »
A thin compliant panel was tested in a Mach 2 wind tunnel. The panel was mounted flush with the tunnel floor and was of dimensions L=121.9 mm (chord), W=63.5 mm (span) and h=0.254 mm (thickness). A 20 degree compression ramp was placed 5 mm downstream of the model, which induced a shock/boundary layer interaction with fully separated flow over parts of the panel. Full-field deformation was measured using Digital Image Correlation and the surface pressure field was obtained from fast-response pressure-sensitive paint. Analysis of the shock foot motion was performed using a curve-fitting method. Comparison of the shock motion between a rigid and compliant panel case showed no difference in the size of the intermittent region but found that the shock motion over the compliant panel is affected by the panel vibration. Proper Orthogonal Decomposition revealed that the surface pressure is dominated by low-frequency unsteady shock motion, in both cases (rigid and compliant panel). The sixth POD mode clearly shows the streamwise shock foot motion oscillates at the first panel vibration frequency. The surface pressure field upstream of the shock foot is dominated by piston-theory aerodynamics and thus correlated to the slope of the compliant panel. The Sparse Identification ofmore »
Experimental Investigation of Flow-Structure Interaction for a Compliant Panel under a Mach 2 Compression-RampThis experimental study focuses on fluid-structure interaction (FSI) for a thin compliant panel under a shock/boundary layer interaction (SBLI) generated by a 2D compression ramp in a Mach 2 wind tunnel. In previous work, we have studied the FSI for this configuration using simultaneous fast-response pressure-sensitive paint (PSP) and digital image correlation (DIC). Simultaneous PSP/DIC allows for examination of the relationship between the dynamic panel displacement and surface pressure loading, respectively. Spectral analysis showed that pressure fluctuations within the interaction region and shock-foot unsteadiness tend to lock to the first mode resonant frequency of the compliant panel. The current study aims to utilize synchronous high-speed stereoscopic PIV (25 kHz) and DIC (5 kHz) techniques to better understand the coupling between the flow field and the panel displacement field. The PIV is obtained in a streamwise-spanwise plane located at 15% of the boundary layer height. Thin compliant polycarbonate panel with thicknesses of 1 mm is utilized, which has a first-mode vibrational frequency of 407 Hz. The 1 mm panel out-of-plane displacement amplitude was up to 15% of the boundary layer thickness. The analysis includes low-pass and band-pass filtering of the velocity data, including the surrogate separation line, and cross-correlation analysis betweenmore »
Effect of Structural Modifications on Vibratory Response of Panel under Ramp-Induced Shock Wave Boundary Layer InteractionThe vibration of a compliant panel under a shock / boundary layer interaction (SBLI) induced by a compression ramp in a Mach 2 flow, is investigated experimentally. The panel is made from brass shim stock of length (streamwise), width (spanwise) and thickness of 122 mm by 63.5 mm by 0.25 mm, respectively. The 20° compression ramp is placed near the downstream edge of the compliant panel, and it creates a shock-induced turbulent separated flow that extends over the downstream 20% of the panel. Large pressure fluctuations occur in the region of the separation shock foot unsteadiness. The pressure fluctuations increase vibration amplitudes of the higher panel modes, especially the second mode, which has an antinode near the shock foot region. In this work, the authors use structural modifications of the baseline compliant panel to mitigate vibrations induced by the large pressure fluctuations of the shock foot unsteadiness. A thin rib is attached in the spanwise direction to the lee side of the panel at the location of SBLI. In one configuration, the rib is attached to the panel using epoxy adhesive, which creates a stiff connection. In another configuration, the rib is attached to the panel via double-sided viscoelastic tape,more »