Simulation of an Evolving Convective Boundary Layer Using a Scale-Dependent Dynamic Smagorinsky Model at Near-Gray-Zone Resolutions
Simulation of an Evolving Convective Boundary Layer Using a Scale-Dependent Dynamic Smagorinsky Model at Near-Gray-Zone Resolutions
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DOI：
10.1175/jamc-d-17-0318.1
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发表时间：
2018-09
影响因子：
3
通讯作者：
G. Efstathiou;R. Plant;Mary‐Jane M. Bopape
中科院分区：
文献类型：
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作者：
G. Efstathiou;R. Plant;Mary‐Jane M. Bopape
采用具有层结效应的尺度相关拉格朗日平均动态Smagorinsky次网格格式，模拟了澳大利亚旺加拉对流边界层在灰色区域(特别是网格长度为25~400m)中的演变过程。与粗粒大涡模拟(LES)场的结果相比较，动态Smagorinsky方法和标准Smagorinsky方法对一阶量和二阶量进行了评估。在LES系统中，次网格方案产生了非常相似的结果，尽管在地表附近有一些微小的差异。在较粗的分辨率下，标准Smagorinsky方法的使用显著延迟了可分辨湍流的开始，延迟随分辨率的增大而增加。相比之下，动态Smagorinsky方案大大改善了自旋，因此也能够在较粗分辨率下保持与LES温度廓线的一致性。此外，湍流的分辨部分很好地再现了从粗粒度场获得的湍流廓线，特别是在近灰度区。随着分辨率的进一步粗化，特别是在地表附近，动力方案确实变得有些过度能量。当测试滤波器开始以未分辨的比例采样时，动态方案达到其在当前配置中的极限，返回非常小的斯马戈林斯基系数。灵敏度试验表明，通过调整Smagorinsky常数以适应变化的流场，并最小化对已分解的湍流结构的耗散影响，动态模型能够适应附加的数值或亚网格扩散的变化。
A scale-dependent Lagrangian-averaged dynamic Smagorinsky subgrid scheme with stratification effects is used to simulate the evolving convective boundary layer of the Wangara (Australia) case study in the gray-zone regime (specifically, for grid lengths from 25 to 400 m). The dynamic Smagorinsky and standard Smagorinsky approaches are assessed for first- and second-order quantities in comparison with results derived from coarse-grained large-eddy simulation (LES) fields. In the LES regime, the subgrid schemes produce very similar results, albeit with some modest differences near the surface. At coarser resolutions, the use of the standard Smagorinsky approach significantly delays the onset of resolved turbulence, with the delay increasing with coarsening resolution. In contrast, the dynamic Smagorinsky scheme much improves the spinup and so is also able to maintain consistency with the LES temperature profiles at the coarser resolutions. Moreover, the resolved part of the turbulence reproduces well the turbulence profiles obtained from the coarse-grained fields, especially in the near gray zone. The dynamic scheme does become somewhat overenergetic with further coarsening of the resolution, especially near the surface. The dynamic scheme reaches its limit in the current configuration when the test filter starts to sample at the unresolved scales, returning very small Smagorinsky coefficients. Sensitivity tests reveal that the dynamic model can adapt to changes in the imposed numerical or subgrid diffusion by adjusting the Smagorinsky constant to the changing flow field and minimizing the dissipation effects on the resolved turbulence structures.