雷诺数对圆柱尾流中被动标量场的影响

Reynolds number effect on passive-scalar characteristics of a circular cylinder wake

本文通过实验研究雷诺数对加热圆柱尾流中温度场的影响.实验中雷诺数Re(≡U_∞d/ν,其中U_∞为来流速度、d为圆柱直径、ν为流体黏度)的取值范围为1200—8600.实验中温度是由直径为0.63μm的冷线探针测量的.实验结果表明,一般而言,雷诺数对整个尾流的标量混合特性有着显著的影响.随着雷诺数的增加,平均标量场向外的扩散速度加快、标量脉动强度增加了但衰减也加快.本文还发现:尾流中似乎存在两个区域,一个位于卡门涡街下游靠后,另一个就是传统的远场自相似区;在这两个区域,某些描述标量和动量的相似关系式近似成立.

The effect of Reynolds number on a passive scalar field is investigated in the turbulent wake of a circular cylinder. The cylinder-diameter-based Reynolds number varies between 1200 and 8600. The temperature difference above the ambient temperature acts as a passive scalar quantity. In general, the Reynolds number is found to have significant influence on the scalar mixing characteristics in the wake flow. When Reynolds number increases, the mean scalar spreads out more rapidly and the scalar variance decays with downstream distance at a higher rate. It is also revealed that if is likely to have two regions where some relations for self-similarity are approximately valid, one is located in the late Karman vortex street and the other is the traditional self-preserving far-wake.