Generalised quasilinear approximations of turbulent channel flow. Part 1. Streamwise nonlinear energy transfer
Generalised quasilinear approximations of turbulent channel flow. Part 1. Streamwise nonlinear energy transfer
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湍流通道流的广义拟线性近似：第 1 部分：流向非线性能量传递
DOI：
10.1017/jfm.2022.59
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发表时间：
2022-02-15
影响因子：
3.7
通讯作者：
Hwang, Yongyun
中科院分区：
文献类型：
--
作者：
Hernandez, Carlos G.;Yang, Qiang;Hwang, Yongyun
广义准线性（GQL）近似（马斯顿等人，物理修订信函，vol.116，2016，104502）被应用于在（是摩擦雷诺数）下的湍流槽道流，重点是流向波数空间中的能量传递。将流动分解为低流向波数组和高流向波数组，前者通过考虑完整的非线性方程求解，而后者则从前者周围的线性化方程获得。随后将GQL近似的性能与QL模型的性能进行比较（托马斯等人，Phys.Fluids，第26卷，2014，105112），其中低波数组仅包含零流向波数。结果发现，QL模型表现出显着减少多尺度行为在给定的适度高雷诺数。这是显着改善的GQL近似，它只纳入了几个流向傅立叶模式到低波数组，它合理地恢复了湍流统计和频谱中的距离从壁缩放。最后，它提出的能量转移从低到高波数组的GQL近似，被称为“散射”机制，取决于中性稳定的领先的李雅普诺夫谱的线性方程组的高波数组。特别是，它表明，如果区分这两个组的阈值波数是足够高的，散射机制可以是完全不存在的，由于高波数组的方程的线性性质。
A generalised quasilinear (GQL) approximation (Marston et al., Phys. Rev. Lett., vol. 116, 2016, 104502) is applied to turbulent channel flow at ( is the friction Reynolds number), with emphasis on the energy transfer in the streamwise wavenumber space. The flow is decomposed into low- and high-streamwise-wavenumber groups, the former of which is solved by considering the full nonlinear equations whereas the latter is obtained from the linearised equations around the former. The performance of the GQL approximation is subsequently compared with that of a QL model (Thomas et al., Phys. Fluids, vol. 26, 2014, 105112), in which the low-wavenumber group only contains zero streamwise wavenumber. It is found that the QL model exhibits a considerably reduced multi-scale behaviour at the given moderately high Reynolds number. This is improved significantly by the GQL approximation which incorporates only a few more streamwise Fourier modes into the low-wavenumber group, and it reasonably well recovers the distance-from-the-wall scaling in the turbulence statistics and spectra. Finally, it is proposed that the energy transfer from the low- to the high-wavenumber group in the GQL approximation, referred to as the 'scattering' mechanism, depends on the neutrally stable leading Lyapunov spectrum of the linearised equations for the high-wavenumber group. In particular, it is shown that if the threshold wavenumber distinguishing the two groups is sufficiently high, the scattering mechanism can be completely absent due to the linear nature of the equations for the high-wavenumber group.