Dissimilar control of momentum and heat transfer in a fully developed turbulent channel flow
Dissimilar control of momentum and heat transfer in a fully developed turbulent channel flow
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DOI：
10.1017/jfm.2011.248
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发表时间：
2011-08
影响因子：
3.7
通讯作者：
Y. Hasegawa;N. Kasagi
中科院分区：
文献类型：
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作者：
Y. Hasegawa;N. Kasagi
湍流动量和热输运之间的雷诺类比的广泛适用性意味着独立地减小或增强表面摩擦和传热的固有困难。在本研究中，我们引入次优控制理论，以实现不同的控制，提高传热，同时保持表面摩擦不会大大增加，在一个充分发展的通道流。Fréchet微分清楚地表明，速度场和温度场对壁吹/吸的响应是完全不同的，这是由于速度是无发散的矢量场，而温度是保守的标量场。这一本质上的区别使我们能够实现不同的控制，即使在流动的平均动量和能量传输方程具有相同的形式。结果表明，优化后的控制输入模态具有流向行波特性。通过探讨类行波控制输入与速度场和温度场之间的相位关系，揭示了类行波控制输入通过两种不同的机制，即直接改变雷诺切应力和湍流热流的相干分量和间接影响非相干分量，通过修改平均速度和温度分布。基于这些结果，提出了一种简单的开环策略，不同的控制和评估。
Abstract A wide range of applicability of the Reynolds analogy between turbulent momentum and heat transport implies inherent difficulty in diminishing or enhancing skin friction and heat transfer independently. In the present study, we introduce suboptimal control theory for achieving a dissimilar control of enhancing heat transfer, while keeping the skin friction not increased considerably in a fully developed channel flow. The Fréchet differentials clearly show that the responses of velocity and temperature fields to wall blowing/suction are quite different, due to the fact that the velocity is a divergence-free vector field while the temperature is a conservative scalar field. This essential difference allows us to achieve dissimilar control even in flows where the averaged momentum and energy transport equations have an identical form. It is also found that the resultant optimized mode of control input exhibits a streamwise travelling-wave-like property. By exploring the phase relationship between the travelling-wave-like control input and the velocity and thermal fields, we reveal that such control input contributes to dissimilar heat transfer enhancement via two different mechanisms, i.e. direct modification of the coherent components of the Reynolds shear stress and the turbulent heat flux, and indirect effects on the incoherent components, through modification of the mean velocity and temperature profiles. Based on these results, a simple open-loop strategy for dissimilar control is proposed and assessed.