下击暴流移动对其水平风速及影响高度的作用

Influence of downburst's translational movement on its horizontal wind speed and impacing height

针对下击暴流整体移动对其水平风速的增大效应,采用数值模拟方法(CFD)得到全尺寸下击暴流不同径向位置的风剖面,并与线性叠加算法得到的水平移动下击暴流的风剖面进行对比,发现线性叠加方法在R/D≤1.1径向区间内不能准确体现下击暴流整体水平移动对沿其整体移动方向上的纵向风速剖面的影响。为此,本文提出了非线性预测方法,准确地得到了下击暴流不同水平移动速度条件下的不同径向位置风剖面;结合风剖面计算该公式与大气边界层风速分布,研究了地表粗糙度、10m高度参考风速、下击暴流初始出流速度等对下击暴流影响高度的作用。结果表明:整体水平移动下击暴流影响高度的最大值出现在R/D≤1.13范围;地面粗糙度增加明显降低了该影响高度;整体移动速度增大显著增加了下击暴流的影响高度。

Accounting for the enhancement of downburst's translational movement on its horizontal wind speed, full-scale numerical simulations are carried out and vertical wind profiles of horizontal wind speeds are obtained at different radial locations. These wind profiles are compared with those calculated based on linear superposition method and it is found that, linear superposition method can't accurately predict the effects of downburst's translational movement on its horizontal wind speed along downburst moving direction. Hence, nonlinear superposition method is investigated and it calculates well the horizontal wind profiles at different radial locations of downbursts with different translations speeds. Then by combining with atmospheric boundary layer wind profile, the influence of ground roughness, reference wind speed at 10 m height, inlet wind speed of downburst, are studied. The results indicate that, the impacting height of downburst with translational movement falls in the radial range of R/D≤1.1; increase of ground roughness deceases the impacting height; translational movement evidently raises the impacting height.