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The problems about the turbulentDFSEMinlet method for non-reacting jet

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Old   April 18, 2019, 12:30
Default The problems about the turbulentDFSEMinlet method for non-reacting jet
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liguangze
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Hi,

I have run a non-reacting case with the initial turbulent inlet boundary condition which was created by the turbulentDFSEM method. However, the results there are no velocity fluctuation (u') in the streamline. I don't know how to deal with this problem.

I would appreciate any help on this matter. Thanks in advance! The cases including the files: 0/ were attached.

The turbulentDFSEMinlet was introduced in this website:
https://www.openfoam.com/releases/op...conditions.php
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Old   January 27, 2020, 04:23
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Marc
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Maybe it's a bit late but the line:

Code:
L        uniform 0;
In your 0/U file defines the lengthscale of your incomming eddies as zero - so there will be no turbulence!


If you used a precursor RANS simulation there are correlations to obtain L from you data. For example for a k-\omega simulation you have that:

L=C_{\nu}^{-1/4}\frac{\sqrt{k}}{\omega}


You can find similar correlations for the model you employed. If you didn't get that data from a precursor RANS, I would suggest looking a two-point correlations to obtain L.
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Old   May 20, 2020, 16:19
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Xiangjie Wang
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Hi Marc,

I encountered the same problem.

Could you please give me some suggestions on how to do the RANS precursor simulation?

I set turbulentDFSEMInlet as my inlet velocity.




My computational domain is a wind tunnel with a 50(streamwise)*27.5(width)*22.5(height).

I have run my simulation with a uniform velocity inlet and the results showed that it could work. But when I changed my inlet boundary condition of U, it couldn't.

After inputing blockMesh and decomposePar, I input:
mpirun -np 12 pisoFoam -parallel.
But it was stuck at the first time step, which showed:
Time = 0.005
Courant Number mean: 0 max: 0


In my simulation, the simulation type is RAS, RAS model is KEpsilon.

I only defined the mean velocity profile in ./constant/boundaryData/inlet directory, and for R and L, I set them to a fixed value.
This is how my inlet boundary of U looks like:

inlet
{
type turbulentDFSEMInlet;
delta 12;
nCellPerEddy 1;
d 1;
R uniform (0.5 0.1 0.1 0.03 0.01 0.01);
L uniform 0.005;
mapMethod nearestCell;
value $internalField;
}


I will appreciate it if you can give me some suggestions!

Thanks!
Xiangjie
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