[oda]

Hi,
It's my first post on this forum. I'm openfoam beginner.

I want to use Reynolds Stress Model (LRR model) in channel flow by using simpleFoam.
But, I get the error. Please give me advice the error.

First, I use k-ε model in channel flow.The model performs ok.
So, "relaxation Factors" change all 0.5.
add Fieldfile (0/R) and change LRR from k-ε.

The result is such as error contents.
I can't understand the cause of error.

-----------------error contents------------------------------------

Time = 0.0001

Courant Number mean: 0 max: 0 velocity magnitude: 0
DILUPBiCG: Solving for Ux, Initial residual = 0.999331, Final residual = 0.000100888, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.999331, Final residual = 0.000100888, No Iterations 1
DICPCG: Solving for p, Initial residual = 1, Final residual = 0.00620118, No Iterations 16
time step continuity errors : sum local = 1.38496e-10, global = -1.68073e-25, cumulative = -1.68073e-25
DILUPBiCG: Solving for epsilon, Initial residual = 1, Final residual = 0.000148364, No Iterations 1
DILUPBiCG: Solving for Rxx, Initial residual = 1, Final residual = 5.38634e-05, No Iterations 1
DILUPBiCG: Solving for Rxy, Initial residual = 1, Final residual = 5.38707e-05, No Iterations 1
DILUPBiCG: Solving for Ryy, Initial residual = 1, Final residual = 5.38678e-05, No Iterations 1
DILUPBiCG: Solving for Rzz, Initial residual = 1, Final residual = 5.38636e-05, No Iterations 1
ExecutionTime = 0.1 s ClockTime = 0 s

Time = 0.0002

Courant Number mean: 1.24654e-08 max: 1.97961e-06 velocity magnitude: 6.21442e-06
Segmentation fault (Core dump)
---------------------------------------------------------------------------

--------------------------------------0/R---------------------------------

FoamFile
{
    version     2.0;
    format      ascii;
    class       volSymmTensorField;
    location    "0";
    object      R;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * /
dimensions      [0 2 -2 0 0 0 0];

internalField   uniform (0 0 0 0 0 0);

boundaryField
{
    bottomWall
    {
        type            zeroGradient;
    }

    topWall
    {
        type            zeroGradient;
    }

    sides1
    {
        type            empty;
    }

    sides2
    {
        type            empty;
    }

    inout1
    {
        type            cyclic;
    }

    inout2
    {
        type            cyclic;
    }
}

Please forgive me my lousy English.
Your help is highly appreciated.

Thanks!

oda

[tiam]

This probably wont fix the error, but shouldn't you set fixedValue 0 as bc on the walls for the Re-stresses?


Sent from my iPhone using CFD Online Forum mobile app

[oda]

Hi tiam!

Thank you for your advice.
I tried that method. But, the same result has come out.

I think that BC is wrong because one step can be calculated.
Is that correct?

Thanks!
oda

[oda]

Hi tiam!

Please forgive my continuous post.
I created a graph of residuals in my calculated channel flow and attached that graph.
But, this graph looks like vibration.
Is this affecting LRR?

Now, relaxationFactors is as follows.


p 0.3;
U 0.7;
k 0.7;
epsilon 0.7;
R 0.7;
nuTilda 0.7;

How should I change it?
Please help me.

oda

[tiam]

Sorry, I dont think I can, I have no experience with such models or how they should behave. Regarding the bc at the walls, zero Re-stresses simply follow from the fact that you have no-slip for the velocity.


Sent from my iPhone using CFD Online Forum mobile app

[oda]

Hi tiam!

I appreciate your advice.Thank you very much.
Please tell me if you understand something.

Thank

oda

[nandhakumar]

hello

Recently I have run a problem using LRR. There is a separate thread in this forum how to run LRR/SCG. please read that forum.
I was using openfoam 4.1.
Instead of giving R as a initial condition try to generate R using utility file. It can be found within your openfoam folder. Then run the file using laminar/any other turbulent model. After running for certain timestep change the model to run LRR. Also reduce all the under relaxation to 0.1 to 0.2. If it is compressible flow keep density relaxation as 0.01-0.05.