Geometry of enstrophy and dissipation, grid resolution effects and proximity issues in turbulence
Geometry of enstrophy and dissipation, grid resolution effects and proximity issues in turbulence
复制标题
DOI：
10.1017/s002211200800476x
复制
发表时间：
2009-02
影响因子：
3.7
通讯作者：
I. Bermejo-Moreno;D. Pullin;K. Horiuti
中科院分区：
文献类型：
--
作者：
I. Bermejo-Moreno;D. Pullin;K. Horiuti
我们进行多尺度非局部几何分析的结构提取的拟能和动能耗散率，瞬时场的数值数据库中的不可压缩均匀各向同性湍流随时间衰减的DNS在一个周期性的盒子。考虑了三种不同的分辨率：2563、5123和10243个网格点，kmax分别约为1、2和4，初始条件相同，Reλ = 77。这允许对针对不同分辨率获得的结构的几何形状进行比较。对于最高的分辨率，涡度拟能和耗散的结构演变在一个连续的分布，从斑点状和适度拉伸的管状形状在大尺度高度拉伸片状结构在小尺度。中间尺度显示了主导地位的管状结构的两个领域，更明显的涡度拟能场。在中小尺度下，耗散场的结构比涡度拟能的结构具有更低的曲率。2563网格分辨率情况（kmax ≤ 1）无法检测到两个视野中较小尺度下高度拉伸片状结构的优势。同样的非局部方法的几何结构的研究，但没有多尺度分解，适用于两个标量场，用于现有的本地标准的排放管和片状结构的湍流，Q和[Aij]+，分别从速度梯度张量的不变量和类似的10243的情况下。这将非局部几何特征和分类添加到这些局部标准中，评估它们在导出特定几何形状中的有效性。最后，我们介绍了一种新的方法来研究不同领域的结构之间的邻近问题，基于几何考虑和非局部分析，考虑到结构的空间范围。我们将其应用到前面研究的四个领域。Q的管状结构主要被[Aij]+的片状结构包围，这些结构出现在更近的距离。对于涡度拟能，中等尺度的管状结构主要被较小尺度的涡度拟能片和相同尺度和较小尺度的耗散结构所包围。第二个贡献的结果从管涡度拟能在较小的尺度出现在较远的距离。不同的配置的复合材料结构。
We perform a multi-scale non-local geometrical analysis of the structures extracted from the enstrophy and kinetic energy dissipation-rate, instantaneous fields of a numerical database of incompressible homogeneous isotropic turbulence decaying in time obtained by DNS in a periodic box. Three different resolutions are considered: 2563, 5123 and 10243 grid points, with kmax approximately 1, 2 and 4, respectively, the same initial conditions and Reλ ≈ 77. This allows a comparison of the geometry of the structures obtained for different resolutions. For the highest resolution, structures of enstrophy and dissipation evolve in a continuous distribution from blob-like and moderately stretched tube-like shapes at the large scales to highly stretched sheet-like structures at the small scales. The intermediate scales show a predominance of tube-like structures for both fields, much more pronounced for the enstrophy field. The dissipation field shows a tendency towards structures with lower curvedness than those of the enstrophy, for intermediate and small scales. The 2563 grid resolution case (kmax ≈ 1) was unable to detect the predominance of highly stretched sheet-like structures at the smaller scales in both fields. The same non-local methodology for the study of the geometry of structures, but without the multi-scale decomposition, is applied to two scalar fields used by existing local criteria for the eduction of tube- and sheet-like structures in turbulence, Q and [Aij]+, respectively, obtained from invariants of the velocity-gradient tensor and alike in the 10243 case. This adds the non-local geometrical characterization and classification to those local criteria, assessing their validity in educing particular geometries. Finally, we introduce a new methodology for the study of proximity issues among structures of different fields, based on geometrical considerations and non-local analysis, by taking into account the spatial extent of the structures. We apply it to the four fields previously studied. Tube-like structures of Q are predominantly surrounded by sheet-like structures of [Aij]+, which appear at closer distances. For the enstrophy, tube-like structures at an intermediate scale are primarily surrounded by sheets of smaller scales of the enstrophy and structures of dissipation at the same and smaller scales. A secondary contribution results from tubes of enstrophy at smaller scales appearing at farther distances. Different configurations of composite structures are presented.