An Experimental Investigation of Shock-Induced Panel Flutter Using Simultaneous PIV and DIC

The vibration of panel structural elements immersed in a supersonic flow is a poorly understood fluid-structure interaction (FSI) that can affect the performance and structural integrity of supersonic aircraft and spacecraft systems. These adverse effects are further amplified when a shock-wave/boundary-layer interaction (SWBLI) is formed over the panel. A better understanding of this phenomenon—referred to as shock-induced panel flutter—is therefore crucial for the design of future high-speed vehicles.An experimental method is developed to study shock-induced panel flutter at Mach 2 using planar particle image velocimetry (PIV) and stereographic digital image correlation (DIC) to obtain simultaneous, full-field structural displacement and flow velocity measurements. High-speed cameras are employed to conduct spectral analyses of the panel’s motion and the low-frequency dynamics of the SWBLI during the interaction. To avoid optical interference between the PIV and DIC systems, an optical isolation system is devised using fluorescent paint, dedicated light sources, and color lens filters. The devised experimental setup is used to study the effects of an impinging oblique shock on the dynamics of a flexible panel during flutter, and the effects on the mean flow separation and interaction length of a SWBLI when a rigid wall is substituted by a compliant plate. The coupling of the panel and SWBLI is also studied, identifying the regions in the flow of maximum correlation between the panel’s motion and the flow velocity fluctuations. The obtained results suggest that the inviscid flow region upstream of the SWBLI may play a significant role in the fluid-structure interaction. In addition, a parametric study is conducted to determine the effects of panel aspect ratio and edge boundary conditions on the three-dimensionality of the panel dynamics. The reported findings serve as a reference for future researchers when designing both experimental and numerical simulations of shock induced panel flutter, particularly if two-dimensional flutter is to be recreated.Aerospace Engineerin

Characterization of shock-induced panel flutter with simultaneous use of DIC and PIV

In this experimental study, panel flutter induced by an impinging oblique shockwave is investigated at a freestream Mach number of 2, using the combination of planar particle image velocimetry (PIV) and stereographic digital image correlation (DIC) to obtain simultaneous full-field structural displacement and flow velocity measurements. High-speed cameras are employed to obtain a time-resolved description of the panel motion and the shockwave-boundary layer interaction (SWBLI). In order to prevent interference between the PIV and DIC systems, an optical isolation is implemented using fluorescent paint, dedicated light sources, and camera lens filters. The effect of the panel motion on the SWBLI behavior is assessed, by comparing it with the SWBLI on a rigid wall. The results show that panel oscillations occur with a maximum amplitude of ten times the panel thickness. The dominant frequencies observed in the panel oscillation (424 Hz and 1354 Hz) match the main spectral content of the reflected shockwave position. A further POD analysis of the panel displacement spatial distribution shows that these two frequency contributions are well captured by the first two POD modes, which correspond, respectively, to a first and a third bending mode shape and account for 92% of the total oscillation energy. The fluid-structure coupling is studied by identifying, in the flow, the regions of maximum correlation between the panel displacement and the flow velocity fluctuations. The results obtained prove that the inviscid flow region upstream of the SWBLI is perfectly in phase with the panel oscillation, while the downstream region has a delay of one quarter of the flutter cycle.Aerodynamic