Turbulent kinetic energy production and flow structures in flows past smooth and rough walls
Turbulent kinetic energy production and flow structures in flows past smooth and rough walls
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流过光滑和粗糙壁的湍流动能产生和流动结构
DOI：
10.1017/jfm.2019.96
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发表时间：
2019
影响因子：
3.7
通讯作者：
P. Orlandi
中科院分区：
文献类型：
--
作者：
P. Orlandi
李和莫泽（J.流体力学）对二维湍流通道的直接数值模拟的文献数据。， vol. 774, 2015, pp. 395-415), Bernardini et al. (J.流体力学。， 2014年第742期，第171-191页),Yamamoto & Tsuji (Phys。[j] .流体力学与工程学报，2018,(1):1 - 2。利用大雷诺数范围内的涡旋翻转时间（$q^{2}/\unicode[STIX]{x1D716}$，其中$q^{2}$为湍流动能的两倍，$\unicode[STIX]{x1D716}$为各向同性耗散速率）与平均变形时间尺度（$1/S$）之间的比值$S^{\ast}$与壁面区域雷诺数有很好的标度关系。尽管湍流动能和各向同性耗散率在壁面附近表现出雷诺数依赖性，但良好的标度是由于涡流周转时间；$S^{\ast}$和$-\langle Q\rangle =\langle s_{ij}s_{ji}\rangle -\langle \unicode[STIX]{x1D714}_{i}\unicode[STIX]{x1D714}_{i}/2\rangle$与流动结构相关联，后者在墙附近也表现出良好的标度。研究发现，湍流动能产生的最大值P_{k}$发生在Q约为0$的层中，即不稳定的片状结构卷起来成为棒状结构的地方。对拉伸应变和压缩应变贡献的$P_{k}$分解表明，两者的贡献具有良好的标度性。然而，当墙和外部结构分开时，良好的结垢效果仍然存在。通过直接模拟两壁面上存在不同类型波纹的湍流流动，得出了相同的统计结果。靠近波峰平面的层内的流动物理与表面形状密切相关，并且已经证明，$ u_bb_0 $（垂直于壁面）波动是改变流动结构、增加阻力和产生湍流动能的原因。
Data available in the literature from direct numerical simulations of two-dimensional turbulent channels by Lee & Moser (J. Fluid Mech., vol. 774, 2015, pp. 395–415), Bernardini et al. (J. Fluid Mech., 742, 2014, pp. 171–191), Yamamoto & Tsuji (Phys. Rev. Fluids, vol. 3, 2018, 012062) and Orlandi et al. (J. Fluid Mech., 770, 2015, pp. 424–441) in a large range of Reynolds number have been used to find that $S^{\ast }$ the ratio between the eddy turnover time ( $q^{2}/\unicode[STIX]{x1D716}$ , with $q^{2}$ being twice the turbulent kinetic energy and $\unicode[STIX]{x1D716}$ the isotropic rate of dissipation) and the time scale of the mean deformation ( $1/S$ ), scales very well with the Reynolds number in the wall region. The good scaling is due to the eddy turnover time, although the turbulent kinetic energy and the rate of isotropic dissipation show a Reynolds dependence near the wall; $S^{\ast }$ , as well as $-\langle Q\rangle =\langle s_{ij}s_{ji}\rangle -\langle \unicode[STIX]{x1D714}_{i}\unicode[STIX]{x1D714}_{i}/2\rangle$ are linked to the flow structures, and also the latter quantity presents a good scaling near the wall. It has been found that the maximum of turbulent kinetic energy production $P_{k}$ occurs in the layer with $-\langle Q\rangle \approx 0$ , that is, where the unstable sheet-like structures roll-up to become rods. The decomposition of $P_{k}$ in the contribution of elongational and compressive strain demonstrates that the two contributions present a good scaling. However, the good scaling holds when the wall and the outer structures are separated. The same statistics have been evaluated by direct simulations of turbulent flows in the presence of different types of corrugations on both walls. The flow physics in the layer near the plane of the crests is strongly linked to the shape of the surface and it has been demonstrated that the $u_{2}$ (normal to the wall) fluctuations are responsible for the modification of the flow structures, for the increase of the resistance and of the turbulent kinetic energy production.