Heat Transfer Enhancement and Vortex Flow Structure Over a Heated Cylinder Oscillating in the Crossflow Direction
Heat Transfer Enhancement and Vortex Flow Structure Over a Heated Cylinder Oscillating in the Crossflow Direction
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DOI：
10.1115/1.2826067
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发表时间：
1999-11
影响因子：
--
通讯作者：
C. Gau;J. Wu;C. Liang
中科院分区：
文献类型：
--
作者：
C. Gau;J. Wu;C. Liang
通过实验研究了加热振荡圆柱的流动结构和传热特性。使用烟雾线进行流动可视化和在气缸周围进行局部传热测量。气缸的激励频率选择在F{sub e}/F{sub n} = 0,0.5, 1,1.5, 2,2.5，和3。这些包括谐波、次谐波、超谐波和非谐波频率的激励。不仅在F{sub e}/F{sub n} = 1时，而且在F{sub e}/F{sub n} = 3时，旋涡脱落与筒体激励同步，大大增强了换热。在驻点及其下游区域和流动尾迹区域同时增强的换热表明，发生在近尾迹剪切层的不同模式的不稳定实际上是在驻点上游较远的地方开始和放大的，这些不稳定在加速流动区被抑制，在减速流动区被重新放大。只要通过筒体的激励放大失稳的主导模态，就可以得到强化传热。在实验过程中，雷诺数在1600 ~ 4800之间变化，振荡幅度与圆柱体直径之比在0.064 ~ 0.016之间变化。«少
Experiments are performed to study the flow structure and heat transfer over a heated oscillating cylinder. Both flow visualization using a smoke wire and local heat transfer measurements around the cylinder were made. The excitation frequencies of the cylinder are selected at F{sub e}/F{sub n} = 0, 0.5, 1, 1.5, 2, 2.5, and 3. These include excitations at harmonic, subharmonic, superharmonic, and non harmonic frequencies. Synchronization of vortex shedding with the cylinder excitation occurs not only at F{sub e}/F{sub n} = 1 but also at F{sub e}/F{sub n} = 3, which can greatly enhance the heat transfer. The simultaneous enhancement of heat transfer at the stagnation point, its downstream region, and the wake region of the flow suggests that different modes of instabilities occurring in the shear layer of the near wake are actually initiated and amplified far upstream in the stagnation point, which were suppressed in the accelerated flow region and re-amplified in the decelerated flow region. As long as the dominant mode of the instability is amplified by the excitation of cylinder, enhancement of heat transfer can be obtained. During the experiments, the Reynolds numbers vary from 1,600 to 4,800, the ratios of oscillation amplitude to diameter ofmore » the cylinder from 0.064 to 0.016.« less