Statistics of a passive scalar in homogeneous turbulence
Statistics of a passive scalar in homogeneous turbulence
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DOI：
10.1088/1367-2630/6/1/040
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发表时间：
2004-04-01
影响因子：
3.3
通讯作者：
Gotoh, T
中科院分区：
文献类型：
--
作者：
Watanabe, T;Gotoh, T
用高分辨率直接数值模拟方法研究了在R-lambda=427和P-lambda=427条件下，Sc=1的被动标量在定常均匀湍流中输运的统计特性.在惯性对流范围内的三维标量谱的Obukhov-Corrsin常数被发现是0.68+/-0.04。证明了当Sc>1时，标量速度三重关联的4/3定律在惯性对流和粘性对流范围内都成立，并发现随着Peclet数的增加，4/3定律逐渐接近。计算了被动标量增量的结构函数及其局部标度指数随分离距离的变化，发现存在两个标度范围：惯性对流标度范围和粘性对流标度范围。在惯性对流范围内的标度指数被发现是小于那些的速度场，不饱和，而他们饱和在约1.5的粘性对流范围内的短距离范围内。与纯标量情况相反，混合标量速度结构函数具有较好的单标度范围。对标量和标量耗散场进行了可视化，并与动能耗散场进行了比较。标量场具有独特的形状，具有大规模的高原，陡峭的悬崖和深谷，台地-峡谷结构。
Statistics of a passive scalar with Sc=1 transported by steady homogeneous turbulence at R-lambda=427 and P-lambda=427 is studied by using high-resolution direct numerical simulation. The Obukhov-Corrsin constant of the three-dimensional scalar spectrum in the inertial-convective range is found to be 0.68+/-0.04. It is proved that the 4/3-law for the scalar-velocity triple correlation holds in both inertial-convective and viscous-convective ranges when Sc>1, and found that the 4/3-law is approached with increase in Peclet number. Structure functions of the passive scalar increment and their local scaling exponents are computed as functions of the separation distance, and it is found that there exist two scaling ranges: the inertial-convective range and a narrow precursory range to the viscous-convective range. The scaling exponents in the inertial-convective range are found to be smaller than those of the velocity field and do not saturate, whereas they saturate at about 1.5 in the short precursory range to the viscous-convective range. It is also found that, contrary to the scalar case, the mixed scalar velocity structure function has a well-developed single scaling range. The scalar and scalar dissipation fields are visualized and compared with the kinetic energy dissipation field. The scalar field has a particular shape with a large-scale plateau, sharp cliff and deep valley, a mesa-canyon structure.