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首页> 外文会议>International Conference on Applied Computational Fluid Dynamics October 17-20, 2000 Beijing China >Rng-based viscoelastic turbulence model and numerical applications
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Rng-based viscoelastic turbulence model and numerical applications

机译：基于Rng的粘弹性湍流模型及数值应用

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A Reynolds stress model being quadratic in the mean strain rate and additionally containing its Oldroyd derivative has been shown to arise naturally from the mode reduction process, when renormalization group theory (RNG) is applied up to second order in the " epsilon expansion" to the suitably stochastically forced Navier Stokes equations. The resoluting anisotropic turbulence model fulfills the principles of Galileian invariance and material objectivity from continuum mechanics. Its mathematical structure is similar to the two-scale DIA model of Yoshizawa, but our model coefficients have been explicitly calculated from theory and they depend smoothly on the local turbulence Reynolds number. Therefore the model may be used over a wide range of different flow regimes. In the high Reynolds number limit, our model becomes identical with the constitutive equation of a viscoelastic fluid (second order fluid). So the proposal of Rivlin, who conjectured more than fourty years ago, that a turbulent Newtonian fluid could be regarded as a non-Newtonian fluid, seems to have received some support. In the high Reynold-snumber case our model is similar to Speziale's, which was established on a purely constitutive basis with empirically adjusted coefficients. The closure of our Reynolds stress model is up to now achieved by means of the RNG K - epsilon model of Yakhot, Orszag, Thangam, Speziale, Gatski. Their modeling of the additional production term present in their dissipation rate transport equation and constituting the main difference between their model and the standard K - epsilon model, may be motivated for small shear rates by means of our Reynolds stress model. From a methodological point of rivew, there are some similarities between our work and the work of Rubinstein and Barton, so our result may be compared with theirs. Our model does contain convective transport terms of the strain rate tensor, which are absent from the model of Rubinstein and Barton, but which they state to be essential in the model of Speziale (surely, they are important in the low-Reynoldsnumber regime); their model fails to fulfill the requirement of material objectivity, ours does. With the aid of the commercial codes FIDAP and STARCD, a first version of our turbulence model has been applied with encouraging results to some turbulent separated flow situations.
机译：当平均归一化群论（RNG）在“ε展开”中应用到二阶时，模态还原过程自然产生了一个平均应变速率为二次且还包含其Oldroyd导数的雷诺应力模型。适当地随机强迫的Navier Stokes方程。解析的各向异性湍流模型满足了连续力学中伽利略不变性和物质客观性的原则。它的数学结构类似于吉泽的两尺度DIA模型，但我们的模型系数已根据理论进行了明确计算，并且它们平稳地取决于局部湍流雷诺数。因此，该模型可用于各种不同的流动状态。在雷诺数上限的情况下，我们的模型与粘弹性流体（二阶流体）的本构方程相同。因此，四十多年前就猜想的里夫林的提议是，可以将湍流牛顿流体视为非牛顿流体，这似乎得到了一些支持。在高雷诺数的情况下，我们的模型类似于Speziale的模型，该模型是在纯本构的基础上建立的，并根据经验进行了调整。到目前为止，我们的封闭雷诺应力模型是通过Yakhot，Orszag，Thangam，Speziale，Gatski的RNG K-epsilon模型实现的。通过我们的雷诺应力模型，对于较小的剪切速率，可以激励他们在其耗散率传输方程中存在的附加生产项建模，并构成其模型与标准K-epsilon模型之间的主要区别。从方法论的角度来看，我们的工作与鲁宾斯坦和巴顿的工作之间存在一些相似之处，因此我们的结果可以与他们的结果进行比较。我们的模型确实包含了应变率张量的对流输运项，这在鲁宾斯坦和巴顿的模型中是不存在的，但是它们在斯佩齐亚莱模型中被认为是必不可少的（当然，它们在低雷诺数体系中很重要）；他们的模型无法满足物质客观性的要求，而我们的模型确实如此。在商业代码FIDAP和STARCD的帮助下，我们的湍流模型的第一个版本已被应用，在某些湍流分开的流动情况下，其结果令人鼓舞。

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