Aerodynamic stability and vibration mechanism of long-span flat roofs with various span to eaves-height ratios

Abstract

Computational fluid dynamics (CFD) based on large eddy simulation (LES) is used to investigate the aerodynamic stability of long-span flat roofs with various span/eaves-height ratios (L/H) in this study. Forced vibration tests, where vibrations are induced in the first antisymmetric mode with various frequencies, are conducted on vibrating as well as rigid roofs with L/H = 3, 6, and 9 to obtain distributions of the wind pressure coefficients. The primary focus is the effect of L/H and that of the approach flow turbulence on the aerodynamic stability of the roof, which is quantified using energy consumption. The work done by the unsteady aerodynamic forces on the vibrating roof during the period of vibration was computed using the time histories of the wind pressures at various points on the roof. Furthermore, fluctuating wind pressures and energy consumption are characterized using complex proper orthogonal decomposition (CPOD) analysis. Finally, the vibration mechanism is discussed based on the energy consumption and convection of the wind pressures obtained from CPOD analysis. The results indicate that smooth flow has a higher probability of inducing aerodynamically unstable vibration than turbulent flow because of the phase excitation.