LARGE EDDY SIMULATION OF THE WIND FIELD AROUND A THREE-DIMENSIONAL HILL BASED ON AN IMPROVED NSRFG METHOD

The accurate synthesis of the inflow turbulence conditions that satisfy the characteristics of prescribed atmospheric turbulent boundary layer wind fields for large eddy simulation (LES) is the key issue in current research for accurately simulating the feature of the wind flow filed around hilly terrain. Based on the NSRFG (narrowband synthesis random flow generation) method, an improved NSRFG (INSRFG) method was put forward by improving the spatial tuning factor γ_j, introducing the time scale correction factor τ₀ and the spectral energy correction coefficient λ_i. The NSRFG method and INSRFG method were used to generate the inflow turbulence conditions for LES to study the applicability of these two methods within the wind field of hilly terrain. Through comparison of the LES results with those of wind tunnel test and the Category B wind field specifications, the effectiveness of the aforementioned two methods in simulating flow fields around 3D hill was investigated. Compared to the NSRFG method, the turbulence wind filed on the inlet surface obtained through the INSRFG method can better satisfy the requirements of the characteristics of the turbulence wind fields, such as the fluctuating wind speed power spectrum, spatial correlation, and temporal correlation. In comparison with the NSRFG method, the simulated mean and fluctuating wind profiles around the three-dimensional (3D) hill by INSRFG exhibits better consistency with the experimental data. Particularly, relative errors between INSRFG simulation and wind tunnel test are smaller on the leeward side of the hill with complex flow patterns. In addition, the variation characteristic of the flow filed structure around the 3D hill is more reasonable, especially on the leeward side of the hill where the multi-scale flow field structure can be better reproduced by the INSRFG method.