本文用离散涡模型与边界层理论相结合的方法,研究了贺柱突然起动后初期和长期阶段中柱后尾流的流动结构和涡旋运动.计算初始阶段不定常边界层分离时,本文提出了一个能耦合外流、尾流作用的估算分离点的简单公式.运动趋于准定常后,边界层分离用Thweites方法计算.文中考虑了二次涡的影响和涡旋的粘性扩散效应. In this paper, the flow structure and vortex motions of the wake of the post-column in the early and long-term phases after sudden start-up of the He column are studied by a combination of the discrete vortex model and the boundary layer theory. At the initial stage of the calculation of the unsteady boundary layer separation, A simple formula that can be used to estimate the separation point of outflow and wake is given. After the movement tends to be constant, the boundary layer separation is calculated by Thweites method. The effect of secondary vortex and viscous diffusion of vortex are considered.