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-   -   Apparent inviscid flow over rectangle problems (https://www.cfd-online.com/Forums/openfoam/80719-apparent-inviscid-flow-over-rectangle-problems.html)

ozzythewise October 4, 2010 14:58

Apparent inviscid flow over rectangle problems
 
1 Attachment(s)
Hi all,

I'm simulating flow over a rectangle at a Reynolds number of 10^5, using upwind discretization scheme, komega turbulent model, water at 20 degrees C as the fluid. I'm expecting to see recirculation just behind the leading edge of the rectangle but I can't see it. Attached is a picture of my stream lines. I'm using a grid set up such that I have a y+ of ~5. From my picture you can see that it looks like my simulation is completely inviscid, which makes no sense to me. Anyone have any ideas?

Thanks
-J

ozzythewise October 5, 2010 16:54

Does anyone have an idea for this?

Thanks
-J

ozzythewise October 6, 2010 07:47

If anyone has any ideas for this I would really appreciate it, I am really stuck on this one. I think the issue is with my wall functions, but I really don't know. Here is my 0/nut file:

dimensions [0 2 -1 0 0 0 0];

internalField uniform 0;

boundaryField
{
inlet
{
type fixedValue;
value uniform 0;
}
outlet
{
type zeroGradient;
}
topAndBottom
{
type symmetryPlane;
}
rectangle
{
type nutWallFunction;
value uniform 0;
}
frontAndBack
{
type empty;
}
}


Does anyone have any ideas to help me out?
Thanks
-Jeff

maddalena October 6, 2010 08:34

Hi Jeff,
how do you define your rectangle patch in constant/polymesh/boundary? it should be wall.
And what about k and omega values? they should be kqRWallFunction and omegaWallFunction.
One more check: what OF version are you using?

hope it helps.
regards

mad

ozzythewise October 6, 2010 08:43

Hi mad,

My rectangle patch is defined as a wall, and I am using the kqRWallFucntion and omegaWallFunction for k and omega respectively. I'm using OF v1.6. Any other thoughts?

-J

ozzythewise October 6, 2010 09:08

Here's another noodle scratcher;

If I plot my wall shear stress at my last time step on the wall (close to the leading edge, x~10% down the wall) I get a value of about 1.8e-5. If however I plot my velocity gradients at the same location, I get a value of 12.5, which if I multiple it by the dynamic viscosity (in this case it's 0.001) I get a wall shear stress value (cause tau_wall = mu * wallGrad) I get a wall shear stress of 0.0125, which doesn't at all match up with 1.8e-5. Can anyone make anything of this?

-Jeff


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