旋转U型通道流动与换热特性的数值研究

应用k-ω SST（shear stress transport）湍流模型，计算分析旋转U型通道在不同进口雷诺数（10000~60000）和高旋转数（0~2.013）范围内的流动与换热特性.结果表明:在静止和旋转状态下，进口雷诺数越大，努塞尔数越大.相比于同一工况下的静止状态，旋转显著增强了径向外流直通道的换热强度，径向内流直通道换热强度增大不明显.旋转数对U型通道换热的影响主要通过改变哥氏力和浮升力的大小.受哥氏力的影响，径向外流直通道后缘面换热增强，前缘面换热减弱.浮升力诱发了近壁面的流动分离，使得径向外流直通道前缘面不同位置处的换热强度随旋转数的增加而先减小后增大，计算得到的临界旋转数变化规律与实验测量结果保持一致，即无量纲距离参数与临界旋转数的乘积为定值. 

Numerical investigation of flow and heat transfer characteristics in rotating square U-duct

k-ω SST (shear stress transport) two-equation turbulence model was used to analyze the flow and heat transfer characteristics in rotating square U-duct at different inlet Reynolds numbers (10000~60000) and rotation numbers (0~2.013). Results show that both in stationary and rotating state, Nusselt numbers are augmented with the increase of inlet Reynolds number. Comparing with stationary state, at the same Reynolds number, the intensity of heat transfer in radial outward passage is dramatically enhanced by rotating, while the radial inward passage is just enhanced a little. Rotation number influences the U-duct heat transfer through changing the values of Coriolis force and buoyancy force. Coriolis force enhances greatly the heat transfer of trailing surface in radial outward passage, while the leading surface weakens. Buoyancy force causes flow separation in the vicinity of the wall, so it alters the heat transfer characteristics. In different positions of the radial inward passage, the heat transfer intensity of the leading surface firstly decreases and then increases with the rise of rotation number. The critical rotation numbers got by calculation are in good agreement with the experimental results. The product of dimensionless distance parameter and critical rotation is a constant.