Forced convection for flow across two tandem cylinders with rounded corners in a channel
Forced convection for flow across two tandem cylinders with rounded corners in a channel
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DOI：
10.1016/j.ijheatmasstransfer.2018.10.125
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发表时间：
2019-03
影响因子：
5.2
通讯作者：
Wei Zhang;Xiao-ping Chen;Hui Yang;H. Liang;Yi-kun Wei
中科院分区：
文献类型：
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作者：
Wei Zhang;Xiao-ping Chen;Hui Yang;H. Liang;Yi-kun Wei
本文首次对Re = 100条件下双圆柱绕流的强迫对流进行了数值研究。两个圆柱体都具有在所有拐角处均为圆形的正方形几何形状，曲率半径为R，其无量纲化为R +=R/D，其中D是圆柱体直径，因此圆柱体几何形状可以是正方形（R+= 0.0）、部分圆形（R+= 0.1-0.4）或圆形（R+= 0.5）。这两个圆柱体在流向上隔开一段距离，其特征是气隙比（GR）的参数选择为GR = 1（1）8。这项工作的目的是探讨两个重要参数的影响，即，间隙比和拐角半径对串联布置的流动不稳定性和换热特性的影响。通过瞬态温度场和涡量场、典型气动量和换热量的变化、局部换热量的空间分布、差距区和近尾迹区的流动特性以及通道壁面温度分布和变化，展示和分析了这两个参数的影响。结果由时间平均和波动量来表示，以反映平均和脉动行为。我们观察到圆柱的几何形状决定了下游圆柱后近尾流的非定常性;对于角半径较小的方形圆柱，流动总是非定常的，而具有较大角半径的圆形圆柱可以稳定流动，从而大大减弱甚至完全抑制小GRs的流动波动。计算结果还表明，小GRs时差距流为定常流，大GRs时为非定常流，可分为定常间隙流区和非定常间隙流区。在差距流动由定常向非定常过渡的临界间隙率处，代表性特征量变化剧烈。GRandR+所划分的不同流型也基本上决定了差距和近尾迹区的流型、圆柱表面换热率的平均值和波动以及通道壁面的温度变化。
This work presents the first numerical investigation on the forced convection of flow across two tandem cylinders with rounded corners in a channel atRe= 100. Both cylinders have the geometry of a square rounded at all corners with a radius of curvatureR, which is non-dimensionalized asR+=R/DwhereDis the cylinder diameter, thus the cylinder geometry can be square (R+= 0.0), partially rounded (R+= 0.1–0.4) or circular (R+= 0.5). The two cylinders are separated at a distance in the streamwise direction as characterized by the parameter of gap ratio (GR) chosen atGR= 1(1)8. The objective of this work is to explore the effects of two significant parameters, i.e., gap ratio and corner radius, on the flow unsteadiness and heat transfer characteristics of the tandem arrangement that has not been studied before. The effects of the two parameters are exhibited and analyzed by the instantaneous temperature and vorticity fields, variation of representative aerodynamic and heat transfer quantities, spatial distributions of local heat transfer rate, flow behaviors in the gap and the near-wake regions, and temperature distribution and variation on the channel wall. The results are presented by time-averaged and fluctuating quantities to reflect both mean and pulsating behaviors. We observed that the cylinder geometry determines the unsteadiness of the near-wake flow after the downstream cylinder; the flow is always unsteady for square-like cylinders where the corner radius is small, while the flow can be stabilized by the circular-like cylinders with larger corner radii that the flow fluctuation is greatly weakened or even fully suppressed at smallGRs. Numerical results also reveal that the gap flow is steady at smallGRs and unsteady at largeGRs, as categorized assteady gap flow regimeandunsteady gap flow regime. There are drastic variations for the representative characteristic quantities at the criticalGRwhere the gap flow transits from steady to unsteady. The different flow regimes categorized byGRandR+also substantially determine the flow patterns in the gap and near-wake regions, the mean and fluctuating of heat transfer rate on the cylinder surface and the temperature variation on the channel wall.