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Old   January 6, 2015, 13:04
Default turbulence problem
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António Pires
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Hello everyone

I'm currently trying to simulate wave propagation within a rectangular flume in order to determine velocity component u in the middle of the flume. I'm using IHFoam

Now i would like to make a run where the "simulationtype" field inside the file "turbulenceProperties" is not laminar so i can get more real results.

So I changed the "simulationtype" field to RASModel and in the "RASProperties" file I put this:

RASModel kEpsilon;

turbulence on;

printCoeffs on;


When I run the case i get the following error in terminal:

blockMesh meshing...
Preparing 0 folder...
Setting the fields...
Running...


--> FOAM FATAL IO ERROR:
cannot find file

file: /home/antonio/IHFOAM/IHFOAM_materials/tutorials/OF222/Klopman2/0/k at line 0.

From function regIOobject::readStream()
in file db/regIOobject/regIOobjectRead.C at line 73.

FOAM exiting

Simulation complete.


What is the problem happening here, anyone can help me?

Thanks everyone
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Old   January 6, 2015, 13:10
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Andrea Bianco
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Hi Antonio,

You need to provide to the code the k boundary value and initial values. To do this you need a k file in the 0 folder, and maybe other files depending on the turbulence model used.

Take a look at the tutorials to see how these files are written.

Best regards,
Andrea
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Old   January 6, 2015, 13:47
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António Pires
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Hi Andrea,

Thank you for the quick reply.

I'll do the k file and look for other information.

Anyway, do you know where can i find which files are needed for each turbulence model?

Thank you,

António
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Old   January 8, 2015, 07:48
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Andrea Bianco
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Hi Antonio,

the best thing you can do to know which physical quantities you need to provide to the code in order to use a turbulence model is to dig into the turbulence model code OR to look at the tutorials.

Please note that is not sufficient to turn on a turbulence model in the RASProperties file to use it, usually.

As an example, the k-eps model would certainly require you to initialize k, epsilon and I guess nut (turbulent kinematic viscosity), and you need to provide boundary condition for them also. But you also need to set appropriate solution schemes and algorithm in fvSchemes and fvSolution for each of them PLUS for any other turbulent quantity that the turbulence model will require (i.e. R?).

Look at the tutorials folder, you will get some useful example. After a very first look I would look for example at incompressible/boundaryFoam/boundaryWallFunctions tutorial.

Best regards,

Andrea
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Old   January 8, 2015, 08:17
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António Pires
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Hi Andrea,

Thanks again for your help

I will definitely take a look at your suggestions!

António
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Old   January 11, 2015, 14:03
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Bruno Santos
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Greetings to all!

Quick tip: see subsection "2.1.8 High Reynolds number flow" in the OpenFOAM User Guide: http://www.openfoam.org/docs/user/cavity.php

Best regards,
Bruno
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Old   January 18, 2015, 05:52
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Bruno Santos
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Hi António,

I hope you don't mind, but I'll answer most of the PM you sent me here on this post, because this question is relevant to the public in general

OK, you're question was how to find out about all possible boundary conditions and wall treatment models available in OpenFOAM, in order to try and deduce which ones are suitable for your problem.
The quick answer is going to seem very cryptic without context: use a "banana".
Yes, it seems ludicrous, but it's actually a funny example that works and is explained in detail on the wiki: http://openfoamwiki.net/index.php/Op...de/Use_bananas
If you Google the following:
Code:
site:www.cfd-online.com/forums "wyldckat" banana
you'll find several occasions where I and other people mention this trick. Here's one such example, which is actually very detailed: SaffmanMeiLiftForce post #9

And that's not all! When you do know the name of the classes, you can easily look for them, as detailed here: http://openfoamwiki.net/index.php/In...hing_for_files
Then it's just a matter of looking at the first big block of description in the header files of each class. For example: https://github.com/OpenFOAM/OpenFOAM...hScalarField.H
But you can also look for it in the code documentation: http://www.openfoam.org/docs/cpp/

Best regards,
Bruno
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