A study of gust wind speed using a novel unsteady Reynolds-Averaged Navier-Stokes model

In this study, a novel unsteady Reynolds-Averaged Navier-Stokes (URANS) model is proposed in conjunction with a prespecified averaging time and turbulent inflow, and a new peak factor that considers the effect of averaging time used in URANS is derived to calculate gust wind speed. Firstly, the URANS incorporated with a prespecified averaging time and turbulent inflow is proposed to predict the time series of wind speed over flat terrain and investigate the variation of higher-order moments and zero-crossing rate at which the fluctuating wind speed changes algebraic sign with the averaging time. The predicted higher-order moments are less sensitive to the averaging time, but the predicted zero-crossing rate slightly decrease with increasing the averaging time due to the moving average effect. Secondly, a new peak factor is proposed to consider the averaging time. Finally, the gust wind speeds over flat terrain and around a single building predicted using the proposed URANS and the new peak factor based on the Hermite model are found to be in good agreement with the LES results, while those predicted by the conventional models deviate more from the LES results.