Abstract A new hybrid meteorological model/engineering LES method was used to analyze a tornado and near-ground turbulence under realistic conditions. The hybrid method estimates high frequency turbulence regeneration in an actual severe storm that has complex thermal conditions in order to alleviate the problem of high frequency component dissipation in meteorological models and generate appropriate field data to investigate near-ground flow and wind loading on buildings. The high frequency regeneration method was validated in the convective boundary layer and the energy spectrum of the velocity field was successfully extended to higher frequency region in good agreement with −5/3 Kolmogorov law. Multi-scale simulations of a tornado were conducted based on meteorological model outputs with three different terrain conditions, including an actual urban building geometry and terrain, and the changes in the main tornado vortex and the interactions with near-ground turbulent field were examined. On roughened surfaces with uniform blocks and buildings, the main tornado vortex was connected to near-ground vertical vortices arising due to the urban geometry. The structure was significantly deformed, splitting into numerous finer vortices below several times the building height. These near-ground vortices create localized sharp pressure drop patterns and also affect the movement of the tornado. These effects of low pressure on buildings were quantitatively analyzed.

中文翻译：

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使用混合气象模型/工程 LES 方法分析龙卷风和近地湍流

摘要 一种新的混合气象模型/工程LES方法用于分析现实条件下的龙卷风和近地湍流。混合方法估计具有复杂热条件的实际强风暴中的高频湍流再生，以缓解气象模型中高频分量耗散的问题，并生成适当的现场数据以研究建筑物的近地流和风载荷。高频再生方法在对流边界层中得到验证，速度场的能谱成功扩展到更高频率区域，与-5/3 Kolmogorov 定律非常吻合。基于具有三种不同地形条件的气象模型输出，对龙卷风进行了多尺度模拟，包括实际的城市建筑几何形状和地形，以及主要龙卷风涡旋的变化以及与近地湍流场的相互作用。在具有均匀街区和建筑物的粗糙表面上，主要的龙卷风涡旋与由于城市几何形状而产生的近地垂直涡旋相连。该结构明显变形，在低于建筑物高度数倍的情况下分裂成许多更细的漩涡。这些近地涡流会产生局部的急剧压降模式，也会影响龙卷风的运动。对这些低压对建筑物的影响进行了定量分析。主要的龙卷风涡旋与由于城市几何形状而产生的近地垂直涡旋相连。该结构明显变形，在低于建筑物高度数倍的情况下分裂成许多更细的漩涡。这些近地涡流会产生局部的急剧压降模式，也会影响龙卷风的运动。对这些低压对建筑物的影响进行了定量分析。主要的龙卷风涡旋与由于城市几何形状而产生的近地垂直涡旋相连。该结构明显变形，在低于建筑物高度数倍的情况下分裂成许多更细的漩涡。这些近地涡流会产生局部的急剧压降模式，也会影响龙卷风的运动。对这些低压对建筑物的影响进行了定量分析。