Numerical simulation of wind turbulence by DSRFG and identification of the aerodynamic admittance of bridge decks

Discretizing and synthesizing random flow generation (DSRFG) is applied to generate inflow turbulence satisfying large eddy simulation (LES) requirements for bridge wind engineering. The variation of the turbulent wind along the computational domain is investigated considering multiple grid sizes and time steps. The aerodynamic admittance functions (AAFs) of a thin plate and two bridge sections are evaluated. Turbulence properties are well maintained from the inlet downstream in the windward direction. The grid resolution minorly affects the along-wind profiles of the mean velocity and turbulence intensity, but it greatly influences the wind spectra. The turbulence energy of the wind spectra may decay in the high-frequency range, which can be improved by applying finer grids and small time steps. Reasonable grid and time step size are suggested to provide stable turbulent wind flow along the computational domain. Fairly good agreement between the estimated AAFs of the thin plate and the Sears function validate the feasibility of LES in predicting the AAFs. The AAFs of the bridge sections are different from the Sears function. The contributions of the longitudinal and vertical velocity components to the buffeting forces are not equal, and it is inappropriate to employ one equivalent AAF for each force component.