[sjorskremer]

Hi,
Anybody that can help me out with the following problem?

I want to simulate turbulence in a 3D channel (steady flow).
The similationtype is RAS and the RASModel is LienCubucKE (nonlinear k-eps)

in the blockMeshDict:
I have setup the bottom, top, left and right as a wall type. The inlet and outlet are setup as a cyclic type. and the following dimensions:

// L:length, H:height, W:width
L 20;
H 0.1;
W 1;

blocks
(
hex ( 0 1 2 3 4 5 6 7) (20 10 100) simpleGrading (1 1 1)
);

In the 0 files:
the U, p, nut, k and epsilon all seem to be setup properly (with cyclic inlet and outlet).


I am using pisoFOAM (mandatory for this assignment). However, a very small dT (0.0005) gives a Courant number of 23 after 1.5 seconds, and increasing the dT leads to the following error:

--> FOAM FATAL ERROR: (openfoam-2406)
Continuity error cannot be removed by adjusting the outflow.
Please check the velocity boundary conditions and/or run potentialFoam to initialise the outflow.
Total flux : 2.2607073
Specified mass inflow : 4.2978406e-08
Specified mass outflow : 0
Adjustable mass outflow : 8.0379753e-17


From bool Foam::adjustPhi(Foam::surfaceScalarField&, const volVectorField&, Foam::volScalarField&)
in file cfdTools/general/adjustPhi/adjustPhi.C at line 110.

FOAM exiting

Now i dont now what i can do to fix it??

[Severus]

Hello,
Do you apply a body force term that drives the flow? If you have cyclic boundary conditions for pressure, you will not have a pressure gradient to drive the flow and hence you need to use meanVelocityForce in fvOptions or fvConstraints file (depending on the version of OpenFOAM you use).

Check these links
https://develop.openfoam.com/Develop...tant/fvOptions
https://github.com/OpenFOAM/OpenFOAM.../fvConstraints
https://caefn.com/openfoam/fvoptions-meanvelocityforce

One other suggestion, instead of specifying deltaT, use adjustTimeStep option and provide a maximum Courant number, so that the solver will adjust the time step so that the maximum
Courant number limit is satisfied.
https://www.openfoam.com/documentati...output-control

Thanks