The importance of non-normal contributions to velocity gradient tensor dynamics for spatially developing, inhomogeneous, turbulent flows
The importance of non-normal contributions to velocity gradient tensor dynamics for spatially developing, inhomogeneous, turbulent flows
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DOI：
10.1080/14685248.2019.1685095
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发表时间：
2019-09
影响因子：
1.9
通讯作者：
P. Beaumard;O. Buxton;Christopher J. Keylock
中科院分区：
文献类型：
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作者：
P. Beaumard;O. Buxton;Christopher J. Keylock
我们研究空间演化湍流（近尾流、两个轴对称射流和平面混合层）的速度梯度张量的属性。重点研究张量的正规部分和非正规部分。非正态性在动力学中发挥的作用比在 HIT 中观察到的作用更大，并且对于所有检查的空间位置也是如此。这意味着压力 Hessian 矩阵的偏差部分起着更大的作用。尾流的结果，我们使用模态分解分离动力学的相干部分，阐明了这些竞争效应如何运作。先前的研究表明，Q-R 图的形状（由张量特征方程的第二个和第三个不变量组成）在小尺度下对于不同的流近似是通用的。 Q-R 方法中忽略了非正态动力学，但流之间的非正态动力学似乎存在显着差异。
We investigate the properties of the velocity gradient tensor for spatially evolving turbulent flows (a near-wake, two axisymmetric jets and a planar mixing layer). Emphasis is placed on the study of the normal and non-normal parts of the tensor. Non-normality plays a greater role in the dynamics than is observed for HIT and does so for all spatial locations examined. This implies a greater role for the deviatoric part of the pressure Hessian. Results for the wake flow, where we isolate the coherent part of the dynamics using a modal decomposition, clarify how these competing effects operate. Previous studies have shown the shape of the Q–R diagram (formed by the second and third invariants of the characteristic equation for the tensor) is approximately universal at small-scales for different flows. The non-normal dynamics are neglected in the Q–R approach but appear to differ significantly between flows.