Dynamics of unsteady heat transfer in pulsating flow across a cylinder
Dynamics of unsteady heat transfer in pulsating flow across a cylinder
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DOI：
10.1016/j.ijheatmasstransfer.2017.02.072
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发表时间：
2017-06
影响因子：
5.2
通讯作者：
A. Witte;W. Polifke
中科院分区：
文献类型：
--
作者：
A. Witte;W. Polifke
本文研究了流速小扰动时圆柱与脉动横流间的非稳态换热。在这种情况下，循环平均传热是恒定的，并且流动变量的波动可以被描述为线性的、时不变的动态。自由流速度突然增加的响应的数值模拟允许可视化和物理解释的流动和传热动力学。宽带激励与线性系统识别相结合，产生定量预测的频率响应的传热在一定范围内的雷诺数和斯特罗哈尔数。结果表明，传热动力学受多个时间尺度的控制，分别对应于速度场和温度场的响应时间。不同的时间滞后的相互作用导致的斯特劳哈尔和雷诺数的传热频率响应的非平凡的依赖。频率响应函数在高Strouhal数时表现出振幅消失的低通特性和略高于-π/2的相位滞后。对于阶数为1的Strouhal数和阶数为10的Reynolds数，观察到高于传热频率响应的准稳态值的过量增益。
The unsteady heat transfer between a cylinder and pulsating cross-flow is investigated for small perturbations of flow velocity. In this regime the cycle-averaged heat transfer is constant and fluctuations of flow variables can be described as linear, time-invariant dynamics. Numerical simulation of the response to a sudden increase of the free stream velocity allows to visualize and interpret physically the flow and heat transfer dynamics. Broadband excitation combined with linear system identification yields quantitative predictions of the frequency response of heat transfer over a range of Reynolds and Strouhal numbers. It is concluded that the heat transfer dynamics are governed by several time scales, corresponding to the response times of the velocity field and temperature field, respectively. The interaction of the different time lags leads to a non-trivial dependence of the heat transfer frequency response on Strouhal and Reynolds numbers. The frequency response functions exhibit a low-pass behavior with vanishing amplitudes and a phase lag slightly above-π/2 at high Strouhal numbers. Excess gain above the quasi-steady-state value of the heat transfer frequency response is observed for Strouhal numbers of order unity and Reynolds numbers of order ten.