Fluid–Structure Interaction of Thin Flexible Structures in Wind-Induced Vibrations

Wind-induced fluid–structure interaction (FSI) in membrane structures can lead to aeroelastic instability, yet experimental studies on closed saddle-shaped configurations remain limited. In this paper, the FSI mechanism of a saddle-shaped closed membrane structure was deeply explored through wind tunnel tests. Particle image velocimetry (PIV) was employed to visualize the flow characteristics, and proper orthogonal decomposition (POD) was applied to decompose the flow field and identify the dominant flow structures. Simultaneously, the aeroelastic response characteristics of the membrane structure were analyzed in both the time and frequency domains. The results show that as the Reynolds number increases, the distance between the shear layer and the membrane surface decreases from 58[Formula: see text]mm to 46[Formula: see text]mm, while the vortex scale diminishes from 36[Formula: see text]mm to 9[Formula: see text]mm. This trend significantly increases the vortex shedding frequency, which in turn intensifies the FSI effects. Consequently, the structural vibration frequencies shift upward (e.g. 5.40[Formula: see text]Hz to 27.92[Formula: see text]Hz in first-order frequency), and the aerodynamic damping ratio declines toward zero, indicating heightened instability risk. Concurrently, the aerodynamic damping ratio progressively declines, approaching zero values. The study reveals a distinct FSI mechanism for enclosed membranes, where the trapped air cavity and strong shear-surface interaction may lead to non-proportional damping and complex modal responses, providing new insights for the design of such flexible systems.