SimScale CAE Forum

Bug in k-epsilon turbulence model


#1

I think there is a bug in the k-epsilon turbulence model. When I used it my simulation crashed after a couple of timesteps. When I downloaded the case I found out that on the bounding box all of the patches (except for the symmetry) had the fixedValue type set for k and epsilon variables. Even the ones with no-slip and pressure outlet boundary conditions set in the GUI. For the same boundary patches using k-omegaSST model the types were (in my opinion correctly) set to zeroGradient.


#2

Hi @akosior,

as always - thanks a lot for reporting. @gholami is looking into it and will get back to you as soon as possible. To be sure: I assume you used the “pre-packaged” boundary conditions “Velocity Inlet”, “Pressure Outlet” etc. and not the custom ones?

On a related note: Which turbulence model will be your preferred one for production work? Are the ones currently integrated sufficient for the work you’re planning to do? We did have some requests for more turbulence models but not really many, so this did not get a high priority so far.

Best,

David


#3

Hi @dheiny,

yes I used the “pre-packed” boundary conditions. For the next run I created a custom totalPressure but it did not help. I did not check whether it had any influence on the bc yet.

In our talks on PERRINN so far we mentioned kE, kwSST (covered) and Spalart–Allmaras (I did not see this one).

Best,
Andrzej


#5

Hi @akosior,

Thanks for the feedback. I just had a look at the most recent PERRINN project in your profile, specifically PERRINN F1 V4, Simulation 1 kE, Run 1. I hope it’s the one you’re referring to, seems to fit your description. I did not find an inconsistency in bc definition. For bounding box faces we have:

zero gradient for solid_0_solid_0_face_0, 1, and 3 (outlet and slip)
wall function for solid_0_solid_0_face_2 (wall)
fixed value for solid_0_solid_0_face_4 (inlet)
symmetry for solid_0_solid_0_face_5 (symmetry)

which appear to be correct. Would you please have a look and let me know if this is the setup you were going for?

Babak


#6

Hi @gholami

Actually I am reffering to Run 2 but they are the same. The problem I was talking about is in the 0/k and 0/epsilon files of the downloaded OF case. In those files faces 0, 1, 2, 3 and 4 all have kqRWallFunction type set but for faces 0, 1, 3 should be (IMO) zeroGradient.

Best,
Andrzej


#7

@akosior, in Run 2, faces 0, 1, and 3 have zero gradient, 2 wall function, 4 fixed value, and 5 symmetry. To be clear, boundary box faces belong to solid_0, so names are solid_0_solid_0_face_*. For example, face 0 is at line 2124. Don’t they match what you expect?

Best,
Babak


#8

0/k from line 2124:
solid_0_solid_0_face_0
{
type kqRWallFunction;
value uniform 0.00375;
}
solid_0_solid_0_face_1
{
type kqRWallFunction;
value uniform 0.00375;
}
solid_0_solid_0_face_2
{
type kqRWallFunction;
value uniform 0.00375;
}
solid_0_solid_0_face_3
{
type kqRWallFunction;
value uniform 0.00375;
}
solid_0_solid_0_face_4
{
type kqRWallFunction;
value uniform 0.00375;
}
solid_0_solid_0_face_5
{
type symmetry;
}

0/epsilon from line 3384:

solid_0_solid_0_face_0
{
type epsilonWallFunction;
value uniform 0.0125;
Cmu 0.09;
kappa 0.41;
E 9.8;
}
solid_0_solid_0_face_1
{
type epsilonWallFunction;
value uniform 0.0125;
Cmu 0.09;
kappa 0.41;
E 9.8;
}
solid_0_solid_0_face_2
{
type epsilonWallFunction;
value uniform 0.0125;
Cmu 0.09;
kappa 0.41;
E 9.8;
}
solid_0_solid_0_face_3
{
type epsilonWallFunction;
value uniform 0.0125;
Cmu 0.09;
kappa 0.41;
E 9.8;
}
solid_0_solid_0_face_4
{
type epsilonWallFunction;
value uniform 0.0125;
Cmu 0.09;
kappa 0.41;
E 9.8;
}
solid_0_solid_0_face_5
{
type symmetry;
}


#9

We do not seem to be looking at the same files. Is this the case we are talking about?

The contents do not match:

0/k @2124:2127
solid_0_solid_0_face_0
{
type zeroGradient;
}

0/epsilon from line 3384:
}
solid_76_solid_76_face_4
{
type epsilonWallFunction;
value uniform 0;
}
solid_76_solid_76_face_5
{…

Obviously different files.


#10

You are right. I downloaded it again and it looks like yours. I checked all of the 3 cases and all look the same. So the question is where did I get the previous file from? This is the only silmulation with kE that I have. There is also another difference between the new and old file. In the old one each entry had values of Cmu, kappa and E while new does not have them.