Abstract

A spectral-based computational algorithm is presented, showing the effects of rotation and curvature on a fluid flow with natural and forced convective heat transfer (CHT) in a rotating curved rectangular channel with an aspect ratio of 3 and curvature ratio ranging from 0.001 to 0.5. The bottom wall of the channel is heated, with cooling from the ceiling; the vertical walls are thermally insulated. The system is rotated about the vertical axis in the positive and negative directions with the Taylor number \(-2500\le Tr \le 2500\) due to a constant pressure gradient force applied in the stream-wise direction. With the numerical computation presented, five branches of asymmetric steady solution curves comprising single-pair to 11-pair vortices are found. The change in the flow state is then evaluated by means of time-evolution computation, and sketching of the phase space of the solutions enables good prediction of the flow transition. It is found that in the case of co-rotation, a chaotic flow turns into a steady-state flow via a periodic or multi-periodic flow. In the counter-rotation case, however, irregular oscillations change directly to a multi-periodic flow. The study shows appearance of maximum 6-pair vortices at a small curvature, 11-pair vortices at a moderate curvature, and maximum 2-pair vortices at strong curvature. It is also observed that the number of secondary vortices reduces as Tr increases. The vortex structure of secondary flows is also shown in bar diagrams for easy visualization of the effect of curvature on the flow evolution. The study shows that the CHT is significantly enhanced by the secondary flow and a chaotic flow boosts the heat transfer more effectively than other physically realizable solutions. Finally, a comparison between the simulated and experimental results is performed and reasonable matching between the two solutions is observed.

中文翻译：

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旋转和曲率比对通过旋转弯曲矩形通道的流体流动和能量分布的影响

摘要

提出了一种基于光谱的计算算法，显示了旋转和曲率对具有自然和强制对流传热 (CHT) 的流体在纵横比为 3 且曲率比范围为 0.001 至 0.5 的旋转弯曲矩形通道中的影响. 通道底壁加热，天花板冷却；垂直的墙壁是隔热的。系统以泰勒数\(-2500\le Tr \le 2500\)绕垂直轴正负方向旋转  由于在流动方向上施加的恒定压力梯度力。通过数值计算，找到了包含单对到 11 对涡的非对称稳态解曲线的五个分支。然后通过时间演化计算评估流动状态的变化，并且解的相空间的草图能够很好地预测流动转变。发现在同向旋转的情况下，混沌流通过周期流或多周期流转变为稳态流。然而，在反向旋转的情况下，不规则振荡直接变为多周期流动。研究表明，在小曲率处出现了最大 6 对涡旋，在中等曲率处出现了 11 对涡旋，在强曲率处出现了最大 2 对涡旋。Tr增加。二次流的涡流结构也显示在条形图中，以便于可视化曲率对流动演变的影响。研究表明，二次流显着增强了 CHT，混沌流比其他物理上可实现的解决方案更有效地促进了传热。最后，对模拟结果和实验结果进行了比较，观察了两种解决方案之间的合理匹配。