内置圆柱对台阶绕流流动及传热特征的影响

Effect of Insert Cylinder on the Flow and Heat Transfer Characteristics Over a Backward-Facing Step

后向台阶流道中内置圆柱的流动传热模型兼具了台阶绕流与钝体绕流的特点。这种复合绕流在工程中极具应用前景。针对这一模型的流动传热问题展开研究,重点分析了不同流向内置位置以及不同圆柱直径时的绕流流动传热特性。结果表明:圆柱的流向位置对主回流区的形态以及下游的流动不稳定性有显著影响,在Xc/S=1时,Nut的局部峰值最大,在Xc/S=8时,整个底面的时均传热最强。圆柱直径对下游流动形态以及旋涡尺度有显著影响,整个台阶底面的时均传热随着圆柱直径的增大先增强后减弱。综合内置圆柱位置与直径大小来看,在Xc/S=8,D=0.6S时,后向台阶内置圆柱绕流表现出了最佳的流动传热性能。

The fluid flow and heat transfer model of backward-facing step flow with a cylinder has the characteristics of step flow and cylinder flow.This kind of compound flow can be widely used in power engineering.The fluid flow and heat transfer in this model are studied.The effects of the streamwise insert position and cylinder diameter are analyzed in detail.The results show that the streamwise position of cylinder has a strong effect on the primary recirculation zone and the downstream flow instability.The maximum local peak value of Nut appears in the case of Xc/S=1.The heat transfer of the whole bottom wall shows the best perfor⁃mance in the case of Xc/S=8.The cylinder diameter has a strong effect on the downstream flow structure and vortex scale.The heat transfer of the whole bottom wall increases and then decreases with the increase of cylinder diameter.Considering the position and diameter of the insert cylinder,the best fluid flow and heat transfer case appears at Xc/S=8 and D=0.6S.