不同旋转轴对矩形通道内湍流与换热影响研究

Research on influence of different rotating axes on turbulent flow and heat transfer in a rectangular duct

对旋转矩形通道(横截面的长宽比b/a=2)内湍流流动和换热进行了大涡数值模拟.基于一种具有二阶精度的不协调混合格式(Adams-Bashforth/Crank-Nicholson)对N-S方程进行离散.采用动态亚格子模型对雷诺应力进行了模拟.湍流雷诺数Reτ和普朗特数Pr分别为400和0.71,旋转数Roτ=0～5.分析了管道横截面内平均速度、平均温度以及湍流强度的分布.结果表明,不同的旋转轴对湍流流动和换热有重要的影响,在高旋转数时,湍流结构在稳定侧和非稳定侧均有明显的变化.在相同旋转数下,与矩形通道绕z轴旋转时相比,系统绕y轴旋转的平均换热系数有所增大.

Turbulent flow and heat transfer in a rectangular duct with cross-sectional aspect ratio b/a =2rotating along its spanwise direction were investigated by large eddy simulation.The unsteady N-S equations were discretized based on the inconsistent fixed scheme（Adams-Bashforth/Crank-Nicholson） with the second-order precision.And the dynamic subgrid-scale model was used to evaluate the Reynolds stresses.The simulations were performed for a Reynolds number of 400,while the Prandtl number（Pr） was assumed to be 0.71.The rotation number was changed from 0to 5. The averaged velocity,temperature and turbulent kinetic energy intensity distribution were analyzed in the cross section of the rectangular duct.The results show that the effects of system rotation with different rotating axes have an important influence on the turbulent flow and heat transfer.It is found that the turbulent flow structure is changed obviously near the stable wall and unstable wall at high rotation number.At the same rotation number,the average heat transfer coefficient of the rotation axis paralleling the yaxis is greater than that of the rotation axis paralleling the zaxis.