对具有平均标量梯度的被动标量的直接模拟  

DIRECT UNMERICAL SIMULATION OF PASSIVE SCALAR WITH A MEAN GRADIENT

作　　者：刘亚明[1] 柳朝晖[1] 贺铸[1] 郑楚光[1] 

机构地区：[1]华中科技大学煤燃烧国家重大实验室,湖北武汉430074

出　　处：《工程热物理学报》2005年第6期1045-1048,共4页Journal of Engineering Thermophysics

基　　金：国家重点基础研究专项经费资助项目(No.G1999022207)

摘　　要：采用直接数值模拟方法,对具有平均标量梯度的被动标量场在稳定、均匀各向同性湍流中的统计特性进行了研究(计算Reλ为25和48,Pr数从0.3到4.0)。模拟结果表明:标量的概率密度函数是高斯分布的;标量耗散率的概率分布是不对称性的,在它的左枝还存在明显的拖尾现象,并非对数正态分布;在Re数相同的情况下,随着Pr数的增加, 沿着平均标量梯度方向上的标量梯度其概率分布的偏斜度是减少的,反映出回归各向同性的趋势,而且在以涡量为条件的标量梯度的偏斜度变化曲线中发现涡量影响的饱和现象,我们认为这是由于涡量通过对标量场小尺度结构进行旋转作用来影响标量场的结果。The statistics qualities of passive scalar in homogeneous, isotropic and stationary turbulence with a mean scalar gradient are investigated via DNS （Reλ 25 and 48, Pr from 0.3 to 4.0 ）. Results show that PDFs of passive scalar in all runs computed are closely Gaussian, and those of scalar dissipation rate, which have an visible prolonged tail in their left parts, depart from the log-normal distribution. With the increment of Pr number, it is found that skewness of scalar gradient in mean scalar gradient direction decreases in runs, which they have the same Reynolds number, and saturated phenomena of influence of vorticity are found at near Batchelor scale. By analyzing the dynamics of scalar gradient, it can be presumed that these results are due to the rotation effect of vorcity, which can effectively promote reorientation of scalar small structures.

关 键 词：被动标量 均匀各向同性湍流 直接数值模拟 

分 类 号：O35[理学—流体力学]