基于WRF与CFD的复杂地形风场多尺度耦合模拟分析

Multi-Scale Simulation on the Wind Field for Complex Terrain Based on Coupled WRF and CFD Techniques

在超高层建筑结构抗风研究中,风场的准确模拟是重要的前提条件。文中综合利用WRF(中尺度天气预报)模式可以模拟高空大气环流、小尺度CFD模拟具备高时空分辨率的特点,选取深圳气象塔周边地带作为一典型丘陵地貌风场研究区域,基于四维数据同化(FDDA)技术的WRF模式,以及平衡态大气边界层CFD模拟,进行这一复杂地形局部风场的多尺度耦合仿真分析。风场仿真结果验证了WRF模拟中AN(分析松弛法)与SAN(近地面分析松弛法)同化方案的适用性,相对而言,AN方案模拟精度更高;相较单一的中尺度WRF模拟,WRF-CFD多尺度耦合模式结果与气象实测数据更吻合,表明多尺度耦合模拟中,由于中尺度WRF模式可为小尺度的CFD模型提供更准确的入口边界条件,并通过网格嵌套实现边界层内的降尺度精细化模拟,从而可以提升风场本身的模拟精度。基于WRF-CFD边界层风场的多尺度耦合模拟将是提高高层建筑结构风效应模拟分析精度的有效途径。

The accurate simulation on the wind field is an important prerequisite for the wind resistance research for the super high-rise buildings.In this research,the mesoscale WRF(Weather Research and Forecast)model,which can simulate high atmospheric circulations,and the CFD simulation,which possesses high spatial and temporal resolutions,were combined together to simulate a typical hilly area around the Shenzhen meteorological tower.Based on the WRF simulation loaded with the Four-Dimensional Data Assimilation(FDDA)technique and the CFD simulation for an equilibrium atmospheric boundary layer flow,the multi-scale wind field simulation analyses for this complex terrain were performed.The simulation result verified the applicability of the Analysis Nudging(AN)scheme and the Surface Analysis Nudging(SAN)scheme in WRF simulation,and it shows the accuracy of AN scheme is relatively higher.Compared with the separate mesoscale WRF simulation,the coupling multi-scale mo-deling results are much closer to the meteorological measurement data.The mesoscale WRF model can provide more accurate inlet boundary conditions for the small-scale CFD models and the downscale refined simulation can be rea-lized through the nesting operation in the mesh interface.Thus the simulation accuracy of the wind field can be improved by employing current multi-scale WRF-CFD simulation technique.This study indicates that the multi-scale simulation on the wind field in boundary layer based on the coupled WRF-CFD technique will be an effective way to improve the accuracy of the wind effect analysis for high-rise buildings.