Effects of grid geometry on non-equilibrium dissipation in grid turbulence
Effects of grid geometry on non-equilibrium dissipation in grid turbulence
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DOI：
10.1063/1.4973416
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发表时间：
2017-01-01
影响因子：
4.6
通讯作者：
Iwano, Koji
中科院分区：
文献类型：
--
作者：
Nagata, Koji;Saiki, Teppei;Iwano, Koji
对4个系列共11个网格，包括单尺度网格和多尺度网格进行了试验，研究了网格产生的湍流的发展和衰减特征。特别关注衰减区的耗散和非平衡特性。对于三次迭代和四次迭代的分形方网格，观察到了较宽的非平衡区。泰勒微尺度波长、积分长度尺度L-u和耗散系数C-epsilon的分布表明，大小网格的简单组合并不能再现由分形方网格实现的拉长的非平衡区。另一方面，一种新的网格--准分形网格，用规则网格代替了分形方网格中较小的分形元(N=2-4)的区域，成功地再现了与分形方网格相似的流场和非平衡性质。这表明，大的正方形网格和不均匀排列的小网格的组合产生了拉长的非平衡区。使用Re-0=t(0)U(无穷大)/nu(其中t(0)是最大栅格杆的厚度，U-无穷大是流入速度，nu是运动粘性)而不是Re-M=MU无穷大/nu(其中M是网格大小)，而不是Re-M=MU无穷大/nu(其中M是网格大小)来更好地折叠耗散系数C-epsilon[P.C.瓦伦特和J.C.Vassilicos，《非平衡湍流的通用耗散标度》，Phys。莱特牧师。108,214503(2012年)]。由AIP出版公司出版。
A total of 11 grids in four families, including single-and multi-scale grids, are tested to investigate the development and decay characteristics of grid-generated turbulence. Special attention has been focused on dissipation and non-equilibrium characteristics in the decay region. A wide non-equilibrium region is observed for fractal square grids with three and four iterations. The distributions of the Taylor microscale lambda, integral length scale L-u, and dissipation coefficient C-epsilon show that a simple combination of large and small grids does not reproduce elongated non-equilibrium regions as realized by the fractal square grid. On the other hand, a new kind of grid, quasi-fractal grids, in which the region of the smaller fractal elements (N = 2-4) of the fractal square grid is replaced by regular grids, successfully reproduce a similar flow field and non-equilibrium nature to that seen in the fractal square grid case. This suggests that the combination of large square grid and inhomogeneously arranged smaller grids produces an elongated non-equilibrium region. The dissipation coefficient C-epsilon is better collapsed using Re-0 = t(0)U(infinity)/nu (where t(0) is the thickness of the largest grid bar, U-infinity the inflow velocity, and nu the kinematic viscosity) as a global/inlet Reynolds number rather than Re-M = MU infinity/nu (where M is the mesh size) [P. C. Valente and J. C. Vassilicos, "Universal dissipation scaling for non-equilibrium turbulence," Phys. Rev. Lett. 108, 214503 (2012)]. Published by AIP Publishing.