获得空间发展槽道流动大涡模拟入口条件的最不稳定波方法

Most-unstable wave method for inlet conditions of large eddy simulations of spatially developing channel flows

在空间发展流动的大涡模拟中，构造有效的入口扰动是关键。该文提出了利用Fourier分析获得流动最不稳定波的方法来确定入口扰动。结果表明，与同均方差的Gauss分布扰动相比，最不稳定波扰动能够显著缩短流动的起涡距离。同时，要达到同样的起涡位置，Gauss分布扰动的均方差是最不稳定扰动的350～500倍。可见，提出的最不稳定波入口扰动能够迅速诱发流动本身的Kelvin Helmholtz不稳定，从而提高模拟空间区域的有效性，减小计算量，节约计算时间。

An effective inlet disturbance is key condition for large eddy simulations of spatially developing flows. A most-unstable wave method was developed for the inlet conditions of large eddy simulations, in which the most-unstable wave is obtained by Fourier analyses of the temporal velocities in the unstable region. For the same root mean square magnitude of the inlet disturbance, the vortex roll up occurs earlier using the most unstable wave than with a random Gaussian inlet condition. For the same vortex roll-up position, the root mean square of the random Gaussian inlet disturbance is 350 ~ 500 times larger than that of the most-unstable wave. Therefore, the results show that the most-unstable wave method for inlet disturbances rapidly excites the Kelvin-Helmhohz instability of channel flows, which will reduce calculational times by reducing the computational domain size.