维向切变流中的非线性对称不稳定

讨论了维向切变流中的非线性对称不稳定问题。中采用绝热无粘的非线性对称扰动方程组，利用多尺度摄动方法分析其不稳定波动的有限振幅特性。研究结果表明：不稳定波的有限振幅在强度上呈现出振荡趋势。无论是超临界切变情况，还是次临界切变情况，对称扰动振幅都随时间呈现出周期性的变化，振荡周期的大小不仅与基本场稳定度参数及波的特性有关，而且还与初始扰动的振幅及其增长率有关。

On problem of nonlinear symmetric instability in zonal shear flow

This paper is focused on the problem of nonlinear symmetric instability in a baroclinic basic flow. The limited amplitude characteristics of unsteady wave were investigated with the aid of equations of adiabatic,inviscid, nonlinear symmetric disturbance and a multi-scale singular perturbation technique. Evidence suggests that the limited amplitude of unsteady wave exhibits an oscillatory trend of its intensity: the amplitude of the symmetric disturbance displays periodical variation both in super- and sub-critical shear case, and the duration of the periods is related not only to the stability parameters of the basic field and wave properties but to the amplitude of initial disturbance and its time-varying change rate as well.