论文标题

主动模型分开混合式摩擦/LES

Active model split hybrid RANS/LES

论文作者

Haering, Sigfried W., Oliver, Todd A., Moser, Robert D.

论文摘要

对复杂流的可靠预测模拟需要一定程度的模型复杂性和鲁棒性,超过了当前雷诺平均的Navier-Stokes(RANS)模型的功能。经常解决的大型涡模拟(LES)通常可以提供必要的功能,但是,对于许多感兴趣的流动,这种模拟在计算上太密集而无法进行常规执行。原则上,能够通过建模和分辨的湍流过渡的混合式运输/LES(HRL)模型将减轻不足和LES费用。但是,除了已经存在于RANS和LES中的HRL方法外,这些HRL方法还导致了许多独特的并发症。这项工作提出了一种旨在克服此类挑战的建模方法。此处提出的方法依赖于将湍流模型分为三个不同的组成部分:两个负责提供未解决的应力或耗散的标准子网格模型角色,而三分之一来通过创建解决的湍流来降低模型长度。该配方使HRL中不必要的混合功能。此外,拆分模型方法都减少了基于简单的基于涡流的模型上的物理 - 焦点负担,并为模型选择提供了方便的灵活性。在分辨率足以支持额外湍流的区域中,在最小的局部分辨运动尺度上产生波动。这种主动强迫将系统驱动到赎金与网格分辨的LE之间的平衡,以分辨和流动的任何组合,而分裂模型配方则阻止了局部破坏总应力。该模型在完全发达的,不可压缩的通道流[1]和周期山[2]上进行了证明,其中证明它可以产生准确的结果并避免常见的HRL缺点,例如模型应力消耗。

Reliably predictive simulation of complex flows requires a level of model sophistication and robustness exceeding the capabilities of current Reynolds-averaged Navier-Stokes (RANS) models. The necessary capability can often be provided by well-resolved large eddy simulation (LES), but, for many flows of interest, such simulations are too computationally intensive to be performed routinely. In principle, hybrid RANS/LES (HRL) models capable of transitioning through arbitrary levels of modeled and resolved turbulence would ameliorate both RANS deficiencies and LES expense. However, these HRL approaches have led to a host of unique complications, in addition to those already present in RANS and LES. This work proposes a modeling approach aimed at overcoming such challenges. The approach presented here relies on splitting the turbulence model into three distinct components: two responsible for the standard subgrid model roles of either providing the unresolved stress or dissipation and a third which reduces the model length scale by creating resolved turbulence. This formulation renders blending functions unnecessary in HRL. Further, the split-model approach both reduces the physics-approximation burden on simple eddy-viscosity-based models and provides convenient flexibility in model selection. In regions where the resolution is adequate to support additional turbulence, fluctuations are generated at the smallest locally resolved scales of motion. This active forcing drives the system towards a balance between RANS and grid-resolved LES for any combination of resolution and flow while the split-model formulation prevents local disruption to the total stress. The model is demonstrated on fully-developed, incompressible channel flow [1] and the periodic hill [2], in which it is shown to produce accurate results and avoid common HRL shortcomings, such as model stress depletion.

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