下击暴流竖直风剖面的时变特征

Study on Time Varying Characteristics of Downburst Vertical Wind Profile

以冲击射流模型作为下击暴流的基本风场模型,基于计算流体动力学方法完成了下击暴流初始出流、下沉、冲击地面和沿地面扩展的全过程数值仿真。在此基础上研究了下击暴流在发生、发展和扩散各个阶段的竖直风剖面的时变特征。结果表明,在下沉气流冲击地面前后,各径向位置的水平风速竖直风剖面呈现显著变化。随着下沉气流冲击地面并沿地面向四周扩展,下击暴流形成的环形涡依次经过距下沉气流冲击地面中心由近至远的各径向位置。随着环形涡远离中心,靠近中心的各径向位置的竖直风剖面形状逐渐保持固定,而远离中心的各径向位置处的竖直风剖面则在环形涡抵达前后发生较大变化。

The impinging jet model was adopted here as the wind filed model for downburst. The transient wind fields during the whole formation and diffusion process of the downburst, including initial outflow, down＆aft, impinging and expansion stages, were simulated using time-filtered Reynolds Averaged Navier-Stokes （RANS） numerical simulation method. Then, the wind profile characteristics were studied during whole formation and diffusion process. The results indicated that,the vertical the time varying wind profile presents significant changes in varies radial positions pre and post the down＆aft impinging on the ground. With the downdraft impinging and extending along the ground, the vertical wind profiles change significantly when the main ring vortex pass different radial positions from close to far away from downburst impinging center. When the main ring vortex is away from the impinging center, the vertical wind profiles remained gradually,while the vertical wind profiles shown significant changes before and after the main ring vortex arrival.