gambit画3d管道的问题

chessyde

我是刚刚开始使用fluent的，现在要在gambit里面画一个3d的管道（pipe），里面有一个节流口（orifice）。
因为是刚刚开始使用，所以不太清楚要怎么画3d的，而且还是管道。
希望各位大虾能够帮帮忙。。。
先谢谢了。

cora

画截面，然后拖拽

higgins

我认为：三维计算比较麻烦，直接算可能出现很多问题，最好先用二维轴截面图试算一下，得到收敛解再试三维的！

chessyde

首先要多谢2楼的朋友的解答。。。
3楼朋友说得很多，3d也很花时间，现在我也是先弄2d的了，先熟悉一下再说。
只是现在我又遇到了两个大问题了
1：我要用RAN或者是LES，但是我在fluent里面找不到呢。
2：我要用fluent找出管道墙壁压力的功率谱密度（power spectral density, PSD），我知道要用FFT啦，但是我不知道能怎么弄个input single file给他，而这个input single file是什么？
再次麻烦大家了。。。先谢谢

Frank

一段有关Fluent中LES的评价
                                      

Commercial CFD software is a relatively new phenomenon, one that really only got underway in the late 1980's. Even now, the typical CFD company is relatively small and closely tied to academia. For a nice list of commercial CFD companies, click here.
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The following, originally posted on CFD Online by "Andy," illustrates the stengths and weaknesses typical of commercial software. Although this concerns FLUENT specifically, similar things could be said of any commercial CFD package. "FLUENT is a general purpose code and can address a wide range of problems in fluid mechanics. Although this generality can be what is needed it is also the key to FLUENT's main failing: it cannot predict particular classes of flows as well as CFD codes written solely for that class of flow. That is, if you are only interested in hypersonic flows then a CFD code written only to solve hypersonic flows can be substantially more accurate and more efficient. However, the costs of working effectively with specialized codes are different to those of working with general purpose codes. It can be higher or lower - the key is usually access to educated people who know what they are doing. Perhaps using a bigger computer, waiting longer for the answers and accepting a higher risk that the answers are misleading is perfectly acceptable. It depends on what you are using the code to achieve. "A personal example: I recently considered proposing FLUENT for a set of LES simulation (it has an LES button and could be driven by relatively inexperienced people). After a phone call with FLUENT it became clear that: "The code is very inefficient requiring around 30 times more computing time per time step than a purpose written code. This figure is very approximate but was based on a real prediction running within FLUENT at the time - I could not believe the computing resource it required. "The low accuracy of the convection terms is a poor choice for LES. i.e. requiring much too fine a grid to match a scheme which uses a more accurate differencing scheme. "It was not possible to generate curvilinear grids of a high enough quality. Related to accuracy of convection terms (or perhaps not given the low accuracy differencing!). "The computer memory requirement was not investigated but it looked to be around 10 times more. "I was not convinced that FLUENT were on top of the problems of near wall treatment for this type of flow since the parameters to control it were not in evidence. "To be fair, I think this should be recognised as something of an extreme example caused by FLUENT adopting low accuracy differencing, unstructured grids and general purpose implicit solvers for a class of flows which are best served by high accuracy differencing, structured grids and very simple efficient solvers. "To conclude, I believe codes like FLUENT can help address a significant range of engineering problems. However, they are best used by people who understand their strengths and weaknesses and they are best not used in isolation."   

Frank

3d的可以直接使用，define-solver-viscous中就有

2d的使用下面的命令

1. (rpsetvar 'les-2d? #t)

复制代码

chessyde

太感谢楼上朋友的解答了，我现在就是用2d的，只是到现在我还是不清楚，怎么弄那个FFT，搞不出PSD啊，真不知道那个input single file是什么？
又要麻烦大家了。。。
先谢了。

zhuangxu2008

楼主 你好 我遇到了和你一样的情况，也要用LES模型，我的模型也是2D的，我在命令框输入rpsetvar 'les-2d? #t，提示是错误的命令，郁闷啊，不知道你是怎么解决的

sky7170

原来还要加小括号   多谢多谢 :@P

xiaoyuer_113

2：我要用fluent找出管道墙壁压力的功率谱密度（power spectral density, PSD），我知道要用FFT啦，但是我不知道能怎么弄个input single file给他，而这个input single file是什么？
回答：你需要在计算的时候把你所要得到的位置的压力进行监控，如图所示，并且要激活write，然后再FFT变换的时候将write的.out文件读入，然后显示即可