Abstract A shear-layer-adapted subgrid length scale is applied to the improved delayed detached eddy simulation using the shear stress transport background model (SST-IDDES). The aim is to assess the combination of the wall-modeled LES (WMLES) branch of the SST-IDDES with the new length scale in computing attached flows, as well as to assess the effect of the new length scale when it is applied to the SST-IDDES for mitigating the “grey area” issue through initiating a dramatic drop of eddy viscosity in the initial region of a free shear layer. The assessment is conducted through simulations of a turbulent boundary layer, a fully developed channel flow, a near-sonic turbulent jet and a backward-facing step flow. The results provide strong evidence for the conclusion that the SST-IDDES combined with the new length scale performs the same as the original SST-IDDES when its WMLES branch is applied to compute the resolved parts of an attached flow, and the combination helps mitigate the “grey area” issue of the SST-IDDES and accurately represent the K-H instability in the initial region of a free shear layer. In addition, the superiority is particularly remarkable for the simulations with coarse grids.

中文翻译：

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SST-IDDES 与剪切层适应的子网格长度尺度对附着和分离流的评估

摘要 使用剪切应力输运背景模型 (SST-IDDES) 将适应剪切层的亚网格长度尺度应用于改进的延迟分离涡模拟。目的是评估 SST-IDDES 的壁面建模 LES (WMLES) 分支与计算附加流中的新长度尺度的组合，以及评估新长度尺度应用于SST-IDDES 通过在自由剪切层的初始区域启动涡流粘度的急剧下降来缓解“灰色区域”问题。评估是通过对湍流边界层、完全发展的通道流、近音速湍流射流和后向阶梯流的模拟进行的。结果为以下结论提供了强有力的证据，即当 SST-IDDES 的 WMLES 分支用于计算附加流的解析部分时，结合新长度尺度的 SST-IDDES 与原始 SST-IDDES 的性能相同，并且该组合有助于减轻SST-IDDES 的“灰色区域”问题，准确表示自由剪切层初始区域的 KH 不稳定性。此外，对于粗网格的模拟，优势尤为显着。