浮升力在竖直通道湍流中的作用

摘要

Statistical quantity in turbulence and turbulence structure were investigated by direct numerical simulation on turbulent flow triggered by different mechanisms in a vertical channel. The statistical results for forced convection, combined convection and natural convection include mean streamwise velocity, mean temperature, intensity of fluctuating velocity and temperature, Reynolds stress, and turbulent structure. The results show that: Compared with forced convection, for combined convection, buoyancy leads to the higher mean velocity and lower intensity of velocity fluctuation near hot wall, but the lower mean velocity and higher intensity of velocity fluctuation near the cold wall; buoyancy results in the stronger temperature fluctuation near the wall regions and the weaker temperature fluctuation in the central part of the channel. Compared with forced convection and combined convection, for the natural convection, the profile of the mean velocity is antisymmetric to the center line, and both the largest velocity fluctuation and the smallest temperature fluctuation occur in the central part of the channel; the maximum value of Reynolds stress also locates in the central part of the channel, and negative Reynolds stresses are near the walls.%采用直接数值模拟方法研究了在不同湍流引发机制作用下竖直槽道湍流中统计量的变化以及湍流结构的变化,分别给出了强迫对流、混合对流和自然对流湍流时平均速度、平均温度、湍流脉动强度、雷诺切应力的统计结果以及湍流结构.结果表明:与强迫对流时相比,混合对流时浮升力作用使高温侧的平均速度升高,速度脉动强度降低,而低温侧的平均速度降低,速度脉动强度升高;浮升力使温度脉动强度在壁面附近区域显著增强,而在通道中心区域变弱.与强迫对流和混合对流的情况相比,自然对流的平均速度分布关于通道中心线反对称,通道中间区域的速度脉动强度最大,温度脉动强度则最小;雷诺应力最大值出现在通道中心区域,而负的雷诺应力产生在壁面附近.