论文标题
国王的神话
The Myth of URANS
论文作者
论文摘要
自1990年代以来，从业人员观察到了模拟中的自发不稳定。一些人建议故意将其用作解决大型湍流结构的方法。但是，迄今为止，没有人为这种不稳定的兰斯（Urans）方法产生理论上的理由。在这里，我们扩展了Speziale和Mhuiris（1989），Girimaji等人的动力学系统固定点分析。 （2006年）创建一个针对Urans动力学的理论模型。将结果与均质各向同性衰减的湍流进行比较。该模型表明，星座可以预测不正确的衰减速率，并且该溶液会随着时间的推移而稳定降低。对强制性湍流的类似分析显示，无论模型参数如何，固定的模型能量约为总能量的30％。可以使用相同的分析来展示如何开始解决这些问题。
Since the 1990s, RANS practitioners have observed spontaneous unsteadiness in RANS simulations. Some have suggested deliberately using this as a method of resolving large turbulent structures. However, to date, no one has produced a theoretical justification for this unsteady RANS (URANS) approach. Here, we extend the dynamical systems fixed point analysis of Speziale and Mhuiris (1989), Girimaji et al. (2006) to create a theoretical model for URANS dynamics. The results are compared to URANS simulations for homogeneous isotropic decaying turbulence. The model shows that URANS can predict incorrect decay rates and that the solution tends towards steady RANS over time. Similar analysis for forced turbulence shows a fixed modeled energy of about 30% of total energy, regardless of the model parameters. The same analysis can be used to show how hybrid type models can begin to address these issues.
