[讨论]二维大涡模拟？！

nuaamh2005

我在用ｆｌｕｅｎｔ做二维单相可压流的大涡模拟，
看了fluent的帮助，但它只讲三维的；设置方面：我不清楚：是不是要用一种普通方法，计算收敛后，再使用大涡模拟计算。
另外，大涡模拟的设置：如：边界条件，solution，还有初始化在设置时要注意什么？
下面是，ｆｌｕｅｎｔ的中文说明和英文帮助，关于大涡模拟的：
10.11.5  LES模型的特殊求解策略
LES涉及对一个适当的网格，使用合适的步长，从一些初始条件中计算一个瞬时解。这个解必须是运行足够长时间后变得与初始条件无关，并且能够确定流动区域的统计资料。
计算LES要遵循以下建议：
1.开始时，假定为薄片状流动计算流动仿真，或使用一个诸如标准 或Spalart-Allmaras的简单的平均雷诺湍流模型。由于这是唯一的初始条件，你需要执行直到流动区域开始收敛。这一步是可选的。
2.当开启了LES模型，FLUENT将自动打开非定常求解选项，并选择二次的隐式公式。你需要设置恰当的步长和必要的求解参数。（瞬时计算的求解参数设置的指导方针参见22.15.1节）对所有方程使用中心差分的空间离散方案。
3.计算LES直到流动变得统计地稳定。检查流动是否完全发展并统计稳定地最好方法是监控流动中选定位置的力和求解变量（例如：速度成分或压力）。
4.使用求解/初始化/初始流动统计文本命令输出初始统计资料。在重新求解前，开启Iterate面板中的Time Statistics下的Data Sampling选项（将在22.15.1节进行介绍）。
5.重复计算直到你得到统计地稳定数据。通过估计在解的范围内平均流动滞留时间（ ， 是解范围的特征长度， 是特征平均流动速度）预先确定模拟的持续时间。
下面提供了设置LES求解参数的说明。
11.12.5 LES-Specific Solution Strategies
Large eddy simulation involves running a transient solution from some initial condition, on an appropriately fine grid, using an appropriate time step size. The solution must be run long enough to become independent of the initial condition and to enable the statistics of the flow field to be determined.
The following are suggestions to follow when running a large eddy simulation:

1.
Start by running a steady state flow simulation using a Reynolds-averaged turbulence model such as standard - , - , Spalart-Allmaras, or even RSM. Run until the flow field is reasonably converged and then use the solve/initialize/ init-instantaneous-vel text command to generate the instantaneous velocity field out of the steady-state RANS results. This command must be executed before LES is enabled. This option is available for all RANS-based models and it will create a much more realistic initial field for the LES run. Additionally, it will help in reducing the time needed for the LES simulation to reach a statistically stable mode. This step is optional.
2.
When you enable LES, FLUENT will automatically turn on the unsteady solver option and choose the second-order implicit formulation. You will need to set the appropriate time step size and all the needed solution parameters. (See Section  26.18.1 for guidelines on setting solution parameters for transient calculations in general.) The bounded central-differencing spatial discretization scheme will be automatically enabled for momentum equations. Both the bounded central-differencing and pure central-differencing schemes are available for all equations when running LES simulations.
3.
Run LES until the flow becomes statistically steady. The best way to see if the flow is fully developed and statistically steady is to monitor forces and solution variables (e.g., velocity components or pressure) at selected locations in the flow.
4.
Zero out the initial statistics using the solve/initialize/init-flow-statistics text command. Before you restart the solution, enable Data Sampling for Time Statistics in the Iterate panel, as described in Section  26.18.1.
5.
Continue until you get statistically stable data. The duration of the simulation can be determined beforehand by estimating the mean flow residence time in the solution domain ( , where  is the characteristic length of the solution domain and  is a characteristic mean flow velocity). The simulation should be run for at least a few mean flow residence times.
Instructions for setting the solution parameters for LES are provided below.
Temporal Discretization
FLUENT provides both first-order and second-order temporal discretizations. For LES, the second-order discretization is recommended.

Define  Models  Solver...

Spatial Discretization
Overly diffusive schemes such as the first-order upwind or power law scheme should be avoided, because they may unduly damp out the energy of the resolved eddies. The central-differencing based schemes are recommended for all equations when you use the LES model. FLUENT provides two central-differencing based schemes: pure central-differencing and bounded central-differencing. The bounded scheme is the default option when you select LES or DES.

Solve  Controls  Solution...

qianzd

在fluent窗口输入命令行(包括括号)：
(rpsetvar ';les-2d? #t)

seimd

LES  做2D问题可以么？

nuaamh2005

可以算二维，网上有人做，但至今，没搞到，相关操作？如：那些设置：边界条件，算法，离散格式，松弛因子，等，我正在算，但总超温，不知该怎么设置，郁闷啊！
谁能执教一下，谢谢！

nuaamh2005

这是我做的一个没有前途的计算，真不知该如何改，互相帮助才有进步！拜托!

nuaamh2005

时过境迁，我现在也开始算三维的了。但还是没搞懂。

奋翔蓝天

现在会了不？我想请教~