Turbulent-laminar coexistence in wall flows with Coriolis, buoyancy or Lorentz forces
Turbulent-laminar coexistence in wall flows with Coriolis, buoyancy or Lorentz forces
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DOI：
10.1017/jfm.2012.224
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发表时间：
2012-08-10
影响因子：
3.7
通讯作者：
Schlatter, P.
中科院分区：
文献类型：
--
作者：
Brethouwer, G.;Duguet, Y.;Schlatter, P.
直接数值模拟的亚临界旋转，分层和磁流体动力学壁有界的流动在大型计算域中进行，侧重于层流和湍流可以稳定共存的参数。在大多数情况下，一个大规模的斜层流湍流模式的政权被确定在开始的过渡，在纯剪切流的情况下。目前的研究表明，这种倾斜的制度可以转移到大的雷诺数R e值通过增加科里奥利，浮力或洛伦兹力的阻尼。我们证明了这种现象在三个不同的流动情况下：平面Couette流与展向气旋旋转，平面磁流体通道流与展向或壁正常的磁场，和稳定分层下的明渠流。湍流模式内的近壁湍流结构总是被发现在完全湍流的情况下，在粘性壁单元的规模，而模式本身仍然是大规模的趋势，对更短的波长增加Re。两个不同的制度被确定：在低雷诺数的模式从一个壁延伸到另一个，而在大雷诺数，他们被限制在近壁区域和通道两侧的模式是不相关的，没有任何占主导地位的大尺度结构的流动的核心是高度湍流。
Direct numerical simulations of subcritical rotating, stratified and magnetohydrodynamic wall-bounded flows are performed in large computational domains, focusing on parameters where laminar and turbulent flow can stably coexist. In most cases, a regime of large-scale oblique laminar-turbulent patterns is identified at the onset of transition, as in the case of pure shear flows. The current study indicates that this oblique regime can be shifted up to large values of the Reynolds number R e by increasing the damping by the Coriolis, buoyancy or Lorentz force. We show evidence for this phenomenon in three distinct flow cases: plane Couette flow with spanwise cyclonic rotation, plane magnetohydrodynamic channel flow with a spanwise or wall-normal magnetic field, and open channel flow under stable stratification. Near-wall turbulence structures inside the turbulent patterns are invariably found to scale in terms of viscous wall units as in the fully turbulent case, while the patterns themselves remain large-scale with a trend towards shorter wavelength for increasing Re. Two distinct regimes are identified: at low Reynolds numbers the patterns extend from one wall to the other, while at large Reynolds number they are confined to the near-wall regions and the patterns on both channel sides are uncorrelated, the core of the flow being highly turbulent without any dominant large-scale structure.