fluent湍流模型技巧

立在时间统计平均的基础上的，考虑的是湍动能和湍流耗散输运方程。

2、对于大涡模拟边界条件的设定，没有什么特别的要求。

FLUENT 提供的湍流模型：

Spalart-Allmaras模型

k-ε 模型

－标准k-ε 模型

－Renormalization-group (RNG) k-ε模型 －带旋流修正k-ε模型

k-ω模型

－标准k-ω模型

－压力修正k-ω模型

－雷诺兹压力模型

Spalart-Allmaras模型

The Spalart-Almares model is a one-equation model that it something in between an algebraic model like the Baldwin-Lomax model and a two-equation model like the k-epsilon model. Since it includes one transported turbulent quantity it has the potential to include at least some history effects (transportation of turbulent energy). It is a more modern model than the BL model, but that is of course not a guarantee that it always produces better results.

The SA model is very robust and is easy to use. For attached flows it often produces good results. It is popular in aero-space applications and for quick design-iteration simulations in the turbo-machinery field. The SA model rarely produces the completely unphysical results that a k-epsilon model can produce sometimes. This has made the SA model quite popular in the last 5 years.

Spalart has also developed a nice DES variant of the SA model, where the large eddies are resolved and the smaller edies are modeled using the SA model. This type of hybrid RANS/LES models have produced very good results for massively separated flows in aerospace applications - there is a very nice example of a SA DES simulation of a stalling F18 which you can probably find on the net if you google a bit. For heat transfer applications I'd not recommend SA. It often under-predicts heat-transfer. 对于解决动力漩涡粘性，Spalart-Allmaras模型是相对简单的方程。它包含了一组新的方程，在这些方程里不必要去计算和剪应力层厚度相关的长度尺度。Spalart-Allmaras模型是设计用于航空领域的，主要是墙壁束缚流动，而且已经显示出和好的效果。在透平机械中的应用也愈加广泛。

在原始形式中Spalart-Allmaras模型对于低雷诺数模型是十分有效的，要求边界层中粘性影响的区域被适当的解决。在FLUENT中，Spalart-Allmaras模型用在网格划分的不是很好时。这将是最好的选择，当精确的计算在湍流中并不是十分需要时。再有，在模型中近壁的变量梯度比在k-e模型和k-ω模型中的要小的多。这也许可以使模型对于数值的误差变得不敏感。 需要注意的是Spalart-Allmaras模型是一种新出现的模型，现在不能断定它适用于所有的复杂的工程流体。例如，不能依靠它去预测均匀衰退，各向同性湍流。还有要注意的是,单方程的模型经常因为对长度的不敏感而受到批评，例如当流动墙壁束缚变为自由剪切流。 应用范围：

Spalart-Allmaras模型是设计用于航空领域的，主要是墙壁束缚（wall-bounded）流动，而