Efficiency of Mixing Forced by Unsteady Shear Flow
Efficiency of Mixing Forced by Unsteady Shear Flow
复制标题
非定常剪切流强制混合效率
DOI：
10.1175/2008jpo3927.1
复制
发表时间：
2009
影响因子：
3.5
通讯作者：
W. Smyth
中科院分区：
文献类型：
--
作者：
R. Inoue;W. Smyth
摘要通过对Kelvin-Helmholtz （KH）不稳定性的直接数值模拟（DNS），研究了混合效率对时变强迫的依赖关系。通过在倾斜坐标系中求解运动方程，并允许倾斜角度随时间变化，设计出与时间相关的强迫场，以再现波状振荡。混合效率Γc被定义为势能增益与耗散的比值，两者都是在一个强迫周期内的平均值，首先通过表征波的参数进行检查：最小理查德森数Rimin和强迫的归一化频率ω/N。研究了雷诺数Re0和初始随机扰动幅值b的影响。在所提出的实验中，Γc在0.21和0.36之间变化，并由两个事件的时间控制：KH巨浪的出现和波状强迫平均切变减速的到来。其中，当强迫支撑的减速阶段…时，Γc高于规范值0.2。
Abstract The dependence of mixing efficiency on time-varying forcing is studied by direct numerical simulation (DNS) of Kelvin–Helmholtz (KH) instability. Time-dependent forcing fields are designed to reproduce a wavelike oscillation by solving the equations of motion in a tilted coordinate frame and allowing the tilt angle to vary in time. Mixing efficiency Γc is defined as the ratio of potential energy gain to dissipation, both averaged over one forcing cycle and first examined via parameters characterizing waves: the minimum Richardson number Rimin and the normalized frequency of the forcing ω/N. The effect of Reynolds number Re0 and the initial random disturbance amplitude b are also examined. In the experiments presented, Γc varies between 0.21 and 0.36 and is controlled by the timing of two events: the emergence of KH billows and the arrival of the deceleration of the mean shear by the wavelike forcing. Here, Γc is higher than a canonical value of 0.2 when the deceleration phase of the forcing suppr...