论文标题
不对称分层剪切不稳定性的动力学
The Dynamics of Asymmetric Stratified Shear Instabilities
论文作者
论文摘要
分层剪切不稳定性的最理想化的研究假设剪切界面和浮力界面是一致的。我们讨论了不对称性在剪切不稳定性演变中的作用。使用线性稳定性理论和直接数值模拟，我们表明，不对称剪切不稳定性均表现出Holmboe和Kelvin-Helmholtz（KH）的不稳定性的特征，并开发了一个框架来确定不稳定性是否更像霍尔姆博（Holmboe）或更多类似KH。此外，不对称的不稳定性会产生不对称的混合，这些混合具有倾覆和冲刷流的特征，并且倾向于重新调整剪切和浮力界面。除了对称KH模拟之外，我们都观察到梯度richardson数字（$ ri_g $）的分布崩溃，这表明不对称降低了KH驱动混合事件的参数依赖性。观察到的湍流动力学对剪切和分层的小规模细节的依赖性对海洋数据的解释具有重要意义。
Most idealized studies of stratified shear instabilities assume that the shear interface and the buoyancy interface are coincident. We discuss the role of asymmetry on the evolution of shear instabilities. Using linear stability theory and direct numerical simulations, we show that asymmetric shear instabilities exhibit features of both Holmboe and Kelvin-Helmholtz (KH) instabilities, and develop a framework to determine whether the instabilities are more Holmboe-like or more KH-like. Further, the asymmetric instabilities produce asymmetric mixing that exhibits features of both overturning and scouring flows and that tends to realign the shear and buoyancy interfaces. In all but the symmetric KH simulations, we observe a collapse in the distribution of gradient Richardson number ($Ri_g$), suggesting that asymmetry reduces the parameter dependence of KH-driven mixing events. The observed dependence of the turbulent dynamics on small-scale details of the shear and stratification has important implications for the interpretation of oceanographic data.
