如何給出足夠的資訊來獲得協助（CFDonline網站轉載）

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An example on how to get proper help following the guideline shown.

I will try to give an example taken purely from my own imagination that show the kind of info I would like in order to help people.

=== 0 ===

Prepare for getting help. cfd-online does not provide large filesize uploads so registering a dropbox/box account and use a public link to the picture/file makes it a lot easier to share files/pics or the full case.

 1 ////////cfdoline並不提供大型檔案的上傳，故而建議上傳到其他網站，使用公開連結來分享代碼 

=== 1 ===

First give it a relevant name in the title of the thread

simpleFoam pipe case diverges

What this little information tells us is that the solver is simpleFoam, the geometry is a pipe and we know that the problem is that it diverges.

///////////首先你得給你的串一個名字。 /////////// 比如說simpleFoam管道流中的發散 ///////////這個題目提供了資訊有：simpleFoam求解器、管道形狀、PDE的發散

 

 === 2 ===
Second give a sketch of the geometry, a screendump of the mesh and maybe even a cut through the mesh. Paraview and the Clip filter works good here.
This helps immensely when trying to visualise the case in others brains.
The "a picture says more than a thousand words" quote springs to mind here

Below is an example of a picture inserted using a public link from dropbox.



Also the first info you need to give is the output from checkMesh put into a log file

checkMesh > checkMesh.log

 Ok now people know that you have a pipe with two bends and that the mesh is fully structured (paraview shows some as tets, but that is a render issue). The dimensions of the pipe is also known now. Also from the header files people know that you are using OpenFOAM version 2.1.x, this is relevant since there can be some bugs in the version used.

=== 3 ===
Ok now we are ready to start identifying the problem.
You know that you have divergence problems and if you have opened just one book about CFD, you know that stability is related to a number of things.

• Mesh -> We get good output from checkMesh so thats ok
• Solver -> This we get from the fvSolution file so upload/link that
• Schemes -> From the fvSchemes file so upload/link that   

This will allow people to see if you have the correct setup for the type of case/mesh you have.

=== 4 ===
Also some good information to give is the output from the terminal, but please don‘t post 10+ iterations. Post only the relevant bits, for example the 2-3 iterations where the solver start to diverge. Another options would be to give the log file as a upload/link. The output can be put into a file using.

simpleFoam > simpleFoam.log 2>&1

Below is an example of two iterations, they don‘t diverge but you get the drift.

Time = 11smoothSolver:  Solving for Ux, Initial residual = 0.0394701, Final residual = 0.00283316, No Iterations 4smoothSolver:  Solving for Uy, Initial residual = 0.0244406, Final residual = 0.00163773, No Iterations 4smoothSolver:  Solving for Uz, Initial residual = 0.211626, Final residual = 0.0144428, No Iterations 4GAMG:  Solving for p, Initial residual = 0.332445, Final residual = 0.0124884, No Iterations 7time step continuity errors : sum local = 0.0803619, global = 0.0111056, cumulative = 0.0907056smoothSolver:  Solving for epsilon, Initial residual = 0.0137779, Final residual = 0.000915039, No Iterations 3smoothSolver:  Solving for k, Initial residual = 0.0205267, Final residual = 0.00103642, No Iterations 4ExecutionTime = 6.07 s  ClockTime = 6 sTime = 12smoothSolver:  Solving for Ux, Initial residual = 0.0966665, Final residual = 0.00756253, No Iterations 4smoothSolver:  Solving for Uy, Initial residual = 0.103096, Final residual = 0.00828772, No Iterations 4smoothSolver:  Solving for Uz, Initial residual = 0.122408, Final residual = 0.00767765, No Iterations 4GAMG:  Solving for p, Initial residual = 0.181939, Final residual = 0.00707472, No Iterations 5time step continuity errors : sum local = 0.0780837, global = -0.0134194, cumulative = 0.0772862smoothSolver:  Solving for epsilon, Initial residual = 0.0127022, Final residual = 0.000977349, No Iterations 3smoothSolver:  Solving for k, Initial residual = 0.0222577, Final residual = 0.00121352, No Iterations 4ExecutionTime = 6.46 s  ClockTime = 7 s

 

=== 5 ===
This might seem like a lot of work, but if you want people to invest time on you, you must invest at least as much time in asking the right question and give sufficient input to allow people to help you.

I‘m sure that if you follow this simple guide you will get the help you need.

 

如何給出足夠的資訊來獲得協助（CFDonline網站轉載）