Experimental investigation of the flow-structure interaction mechanism of flutter for an 8:1 rectangular flat plate

Abstract

The intrinsic interaction mechanism of flutter between the flow and structure of a rectangular plate remains a mystery from the viewpoint of unsteady flow. The present study provides a novel insight into this interaction mechanism based on an adequate understanding of the formation and evolution of the flapping leading-edge vortex (LEV). A series of wind tunnel tests was conducted to investigate the nonlinear flutter instability of an 8∶1 rectangular plate. The complete flow fields around the model throughout the flutter process were obtained by a particle image velocimetry (PIV) technique using two synchronous cameras with an interpolation and resampling method. To acquire the flow structures corresponding to the characteristic frequency of flutter, the spectral proper orthogonal decomposition (SPOD) method was extended to a noninertial frame to reconstruct the low-rank flow field during flutter and extract the characteristic flow pattern coupled with oscillations. It was found that when the 8∶1 rectangular plate undergoes flutter, the LEVs exhibit a periodic flapping phenomenon induced by the structure oscillations. A two-dimensional correlation analysis of the flapping LEVs was conducted for different inflow velocities. The results demonstrate that there is a substantial phase lead phenomenon in the LEV evolution downstream for a higher inflow velocity. This phenomenon may be related to a phase offset of aerodynamic forces, and finally, it gives rise to flutter.

Keywords

flutter / aerodynamic instability / fluid-structure interaction / leading-edge vortex (LEV) / spectral proper orthogonal decomposition (SPOD)

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Funding

National Natural Science Foundation of China(52178470)

National Key Research and Development Program of China(2022YFC3005303)