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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。
Taking the impinging jet model as the basic wind field model of the downburst, a numerical simulation of the whole process of the initial outflow, sinking, impacting and ground spreading of the downburst was completed based on computational fluid dynamics. On this basis, the time-varying characteristics of the vertical wind profile of the downburst at various stages of occurrence, development and diffusion are studied. The results show that the vertical wind profile of horizontal wind velocity at each radial position shows significant changes before and after the descending airflow impinges on the ground. As the descending airstream strikes the ground and expands all the way around the ground, the annular vortex formed by the downburst passes through each radial position from near to far away from the center of the ground which descends the airflow. As the annular vortex moves away from the center, the shape of the vertical wind profile at each radial position close to the center gradually remains fixed while the vertical wind profile at each radial position away from the center changes greatly before and after the annular vortex arrives.