Spatiotemporal characteristics of flow-structure interaction during transition to aeroelastic instability

Aeroelastic instability occurs when an elastic structure becomes dynamically unstable due to fluid flow, affecting aircraft wings, bridges, buildings, and automobiles. Analyzing fluid behavior is critical for understanding the coupled effects of flow-structure interactions, improving designs, and developing control strategies to mitigate aerodynamic loading effects. We experimentally investigate the spatiotemporal flow characteristics when an elastic cantilever is placed in a jet with relatively low turbulence intensity (<5%). As the Reynolds number increases, the structural oscillation transitions from low amplitude aperiodic to high amplitude limit cycle oscillations. The flow from experiments with the elastic structure is compared with that with a rigid structure with the same geometry to delineate the effect of the elasticity. For the rigid structure, the flow field displays classical shear-layer oscillations with a frequency that scales with the shear-layer thickness. For the elastic structure, however, the flow locks in with the natural frequency of the structure, leading to different spatiotemporal dynamics. We perform frequency wavenumber analysis to quantify the spectral condensation during the transition to limit cycle oscillation. We perform Spectral Proper Orthogonal Decomposition on the velocity field to extract the spatiotemporal coherent structures.