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This 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 between panel displacement and velocity. The results indicate a clear coupling of the panel motion and velocity field, but the spectral analysis suffers from limited time records associated with the pulse-burst laser used for PIV. Future work will focus on collecting more data to improve the statistical convergence of the results. 

The 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, which adds significant damping to the system. The panel vibration and surface pressure field are measured using stereoscopic digital image correlation and pressure sensitive paint. Results show that especially the second vibration mode of the panel is reduced through the addition of the rib. This effect is more pronounced in the case where the viscoelastic tape was used, where a 72% reduction in vibration is observed. 

Background The USA must publicly share information about harmful and potentially harmful constituents (chemicals) in tobacco products. We sought to understand whether webpages with chemical information are “understandable and not misleading to a lay person.” Methods Participants were a national probability sample of US adults and adolescents ( n =1441, 18% smokers). In an online experiment, we randomly assigned participants to view one of the developed webpages (chemical names only, names with quantity ranges, names with visual risk indicators) or no webpage in phase one (between subjects). Participants completed a survey assessing knowledge, misunderstanding, perceived likelihood, perceived severity of health effects from smoking and quit intentions (smokers only). In phase two (within subjects), participants viewed all three webpage formats and reported webpage perceptions (clarity, usability, usefulness) and perceived impact (affect, elaboration, perceived effectiveness). Results In phase one, viewing any webpage led to more knowledge of chemicals (48%–54% vs 28% no webpage, p s<0.001) and health harms (77% vs 67% no webpage, p s<0.001). When exposed to any webpage, 5%–23% endorsed misunderstandings that some cigarettes are safer than others. Webpage format did not affect knowledge or reduce misunderstandings. Viewing any webpage led to higher perceived likelihood of experiencing health effects from smoking ( p < 0.001) and, among smokers, greater intentions to quit smoking ( p =0.04). In phase two, where participants viewed all formats, a visual risk indicator led to the highest perceived impact. Conclusions Knowledge of chemicals and health effects can increase after viewing a website. Yet, websites may not correct the misunderstanding that some cigarettes are safer.