Direct numerical simulation of Taylor-Couette flow subjected to a radial temperature gradient
Direct numerical simulation of Taylor-Couette flow subjected to a radial temperature gradient
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DOI：
10.1063/1.4935700
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发表时间：
2015-12
影响因子：
4.6
通讯作者：
Hao Teng;Nan-Sheng Liu;Xi-yun Lu;B. Khomami
中科院分区：
文献类型：
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作者：
Hao Teng;Nan-Sheng Liu;Xi-yun Lu;B. Khomami
直接数值模拟研究了存在径向温度梯度的两个旋转同轴圆柱之间的泰勒-库埃特（TC）流动。具体而言，研究了浮力和外筒旋转对半径比η = 0.912的湍流TC流系统的影响。对于Rei（内柱）=1000,Reo（外柱）=100的同向旋转TC流，通过增大表示浮力与惯性力之比的参数σ，实现了向强湍流的过渡通道。这种非线性流动转换包括4种有趣的状态，它们依次出现：σ = 0时的混沌波状涡流，σ = 0.02和0.05时的波状互穿螺旋流，σ = 0.1和0.2时的间歇湍流螺旋流，σ = 0.4时的湍流螺旋流。总的来说，流体运动从以大尺度波状泰勒涡（TVs）为特征的离心驱动流动模式转变为以小尺度湍流涡为特征的浮力主导流动模式。湍流统计和传热的相应变化被认为是大尺度电视环流减弱和湍流运动增强的结果。此外，考虑了外柱旋转变化的影响，−500 < Reo < 500存在浮力（σ = 0.1）， Rei = 1000。具体地说，这种变化强烈地影响了方位角和轴向的平均流动，而对波动流体运动的影响较小。特别有趣的是，这里是外壁附近的湍流动力学，在强反旋转区（Reo = - 300和- 500），湍流强度显著降低，雷诺兹应力srrz出现符号反转。为此，已经表明，这种剧烈变化的潜在流动物理与径向和轴向波动运动之间相关性的变化有关。然后，讨论了这种修正对平均轴流、湍流统计、力平衡以及湍流产生和消散等动态过程的有趣影响。
Direct numerical simulations have been performed to study the Taylor-Couette (TC) flow between two rotating, coaxial cylinders in the presence of a radial temperature gradient. Specifically, the influence of the buoyant force and the outer cylinder rotation on the turbulent TC flow system with the radius ratio η = 0.912 was examined. For the co-rotating TC flows with Rei (inner cylinder) =1000 and Reo (outer cylinder) =100, a transition pathway to highly turbulentflows is realized by increasing σ, a parameter signifying the ratio of buoyant to inertial force. This nonlinear flow transition involves four intriguing states that emerge in sequence as chaotic wavy vortexflow for σ = 0, wavy interpenetrating spiral flows for σ = 0.02 and 0.05, intermittent turbulent spirals for σ = 0.1 and 0.2, and turbulent spirals for σ = 0.4. Overall, the fluid motion changes from a centrifugally driven flow regime characterized by large-scale wavy Taylor vortices (TVs) to a buoyancy-dominated flow regime characterized by small-scale turbulentvortices. Commensurate changes in turbulence statistics and heat transfer are seen as a result of the weakening of large-scale TV circulations and enhancement of turbulentmotions. Additionally, the influence of variation of the outer cylinder rotation, −500 < Reo < 500 in presence of buoyancy (σ = 0.1) with Rei = 1000, has been considered. Specifically, it is demonstrated that this variation strongly influences the azimuthal and axial mean flows with a weaker influence on the fluctuating fluid motions. Of special interest, here are the turbulent dynamics near the outer wall where a marked decrease of turbulence intensity and a sign inversion of the Reynolds stressRrz are observed for the strongly counter-rotating regimes (Reo = − 300 and −500). To this end, it has been shown that the underlying flow physics for this drastic modification are associated with the modification of the correlation between the radial and axial fluctuating motions. In turn, the intriguing effects of this modification on the mean axial flow,turbulent statistics, force balance, and dynamic processes such as turbulence production and dissipation are discussed.