Effects of free-stream turbulence on motion-induced aerodynamic forces of a long-span flexible flat roof using LES simulations

This study aims to investigate the effects of free-stream turbulence on motion-induced aerodynamic forces of a long-span flexible flat roof. Large-eddy simulations (LES) of both rigid and forced vibrating roofs under different free-stream turbulence conditions are performed to obtain the aerodynamic forces and flow field data simultaneously. Firstly, the LES simulations of the rigid and vibrating roofs are validated against the reference experiments. And then, characteristics of the distributed pressures on vibrating roofs under free-stream flow turbulence conditions with different turbulence intensities are elucidated. Moreover, the motion-induced forces acting on the vibrating roof under different turbulence conditions are identified and compared, in which the power spectra of wind forces and aerodynamic damping and stiffness are examined. Furthermore, the underlying flow mechanism of the turbulence effects on the motion-induced forces is investigated based on POD analysis of the flow around the vibrating roof. It is found that dual effects exist between the influences of free-stream turbulence and roof motion on the aerodynamic forces, the motion-induced aerodynamic forces on the roof would be greatly decreased with the increase of free-stream turbulence, and the motion-induced effects become less dominant under high free-stream turbulence. The outcomes of this study would facilitate our understanding of the role played by the motion-induced aerodynamic forces and improve the wind-resistant design of long-span roof structures for engineering practices.