圆柱尾迹影响下近壁湍流低速条带的特征

Characteristics of low-speed streaks in near-wall turbulence as disturbed by cylinder wakes

利用氢气泡流动显示方法,对圆柱尾迹影响下的湍流边界层近壁区的低速流体条带特征进行了观察和分析。结果表明:与没有尾迹扰动的情况相比,在圆柱下游低速条带的平均展向间距减小,圆柱距离壁面较近时这种减小更显著,可达到22％;而当圆柱离壁面较远时,尾迹对条带平均间距的影响减弱,其最大减小量的出现向下游推迟。另一方面,尾迹的作用并未使条带间距的统计分布性质发生改变,它们仍然符合对数正态规律。

The characteristics of low-speed streaks in the near-wall region of turbulent cylinder wake/ boundary layer interacting flows are investigated employing hydrogen bubble flow visualization. The results indicate that, in comparison with the undisturbed boundary layer, the mean spanwise streak spacing is reduced downstream of the cylinder. This reduction is particularly marked when the cylinder is close to the wall, and the maximum local spacing reduction reaches 22 % for the experimental conditions. Whereas, raising the cylinder farther from the wall weakens its influence upon streak spacing, and delays the point of maximum reduction downstream.On the other hand, the probability distribution behavior of the streak spacing is not changed by wakes, conforming to lognormal distribution.