The dynamic behavior of flexible membrane roofs in surrounding fluid flows involves complex fluid−structure interactions (FSIs), which would lead to vortex resonance and even aeroelastic instability. In this paper, the FSI effects of saddle-shaped membrane roofs in laminar flows over a range of wind velocities and wind directions are investigated, by simultaneously applying a high-resolution particle image velocimetry (PIV) system and laser displacement sensor in wind tunnels. The flow field is visualized by the PIV system and analyzed in the view of the spatiotemporal evolution of flow velocity and vorticity, as well as the proper orthogonal decomposition analysis. Then, the structural dynamic response is investigated in terms of displacement statistics and dynamic characteristics, and finally the FSI mechanisms are revealed. The results show that both wind velocity and wind direction have a significant effect on the leading-edge separation, especially in the case of larger wind velocity and 45° wind direction. The increasing wind velocity would result in the unstable leading-edge separated shear layer, reduced vortex diameter, and increased vortex shedding frequency. Consequently, the leading-edge separation intensifies the vibration of the membrane roof, which could increase the vibration frequency, the average and maximum displacement by a factor of 3 to 4, and the standard deviation value by a factor of 3 to 5. The vortex-induced resonance appears at the wind velocity of 20 m/s and wind direction of 0°, featuring the sharp increase in displacement, negative aerodynamic damping, and frequency lock-in.
Li et al. (Fri,) studied this question.