Numerical study of turbulent flows over complex terrain using an unsteady Reynolds-averaged Navier-Stokes model with a new method for turbulent inflow generation

In this study, an unsteady Reynolds-Averaged Navier-Stokes (URANS) model with a prespecified averaging time and a new method for turbulent inflow generation is proposed to predict turbulent flows over complex terrain. Firstly, the effect of grid resolution on turbulent flows over complex terrain is investigated by the Reynolds-Averaged Navier-Stokes (RANS) and the URANS models. URANS improves the accuracy of the predicted mean velocity and standard deviation by using finer grids, but the improvement by RANS is limited. Furthermore, the turbulent flows over hills with different slopes predicted by URANS are examined with respect to various averaging times. An optimal averaging time based on the slope of the hills is recommended considering the prediction accuracy and computational efficiency of URANS. Finally, turbulent flows over complex terrain in coastal areas are investigated by URANS and validated by wind tunnel tests. The predicted mean and standard deviation of streamwise velocity over complex terrain by URANS are in good agreement with the experimental data, while those by RANS are overestimated or underestimated. • An URANS model with a new turbulent inflow generation method is proposed to predict turbulent flows. • An optimal averaging time based on TSI is recommended considering accuracy and efficiency. • The predicted mean and turbulent flow fields over complex terrain agree well with experiments.