BC set at fixedValue (0 0 0), but I get a non-zero velocity @ wall
Hi Foamers,
I have the following problem: At the moment, I'm performing simulations of the flow through a pipe by using rhoTurbFoam. I made an axi-symmetric mesh in Gmsh and converted it to OpenFoam. At the wall, which I've defined as "wall" in the boundary dict, I've specified the velocity as: fixedValue, uniform (0 0 0) Everything works fine, but when I look at the resulting data in paraview I see a non-zero velocity at the wall. Why? How? I've tried a couple of things, but nothing seems to work. - specifying the sides as symmetryPlane - speciying the sides as wedge - refining the mesh - different rotation (extruding) direction The steps I did: - Surface in Gmsh - Extrude surface + mesh around the axis - gmshToFoam - define patches - define BC's Who can help me out here? |
You are probably looking at interpolated values.
Try to visualize the "U" field in the cells (it is the one with a sort of cube as icon in the drop-down list in paraview) Francesco |
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But I'd already tried that and it actually makes it worse ;) |
Ok, an update!
When I look at my complete "part", I see non-zero velocities at the wall. When I only import the wall in paraview, I see zero velocity at the wall. So, everything seems to work fine....but the post-processing is a bit strange imo. What is causing this behaviour? How can I make sure that paraview shows me the correct values at the wall? |
I'm still not satified with the results.
When I look at the results of the pitzDaily tutorial, I clearly see that the velocity at the wall is 0. So I don't think I can blame Paraview Is the problem causes by Gmsh and the conversion to OpenFoam? How can I get rid of it? (don't say: "stop using Gmsh") |
Hi Squadron,
have you solved your Problem yet? I´ve got the same Problem here. I converted my Mesh from Gambit to OF and used the makeAxialMesh utility. All worked fine, but i´ve got a non zero velocity at my Wall same as you. Any suggestions? Linh |
Hi Linh,
I'm still not sure, but I think this problem is caused by Gmsh or by me, doing something wrong in Gmsh. Maybe you can try blockmesh. I'm now working on an other project, I won't be working with Gmsh anymore. Age |
Hallo,
I built a mesh with blockMesh and converted it with makeAxialmesh to axissymmetric. I plotted the velocity-profils and I get nonzero values at wall boundaries, too. My inlet velocity is about 0.265 m/s and directly at the wall the vellocity is 0.08 m/s by using the sample utility. I even changed the writePrecision from 6 to 10 in the controldict, but nohting changed. Anybody an idea? Thanks a lot Thomas |
Hello Age,
It's been quite some time since you reported your problem in cfd-online. I am getting the same wrong data at wall with OF-2.1.x, were you ever able to fix that problem? I need to run some other code on a 2D plane with the data of my axisymmetric simulation, with the proper BC's values. I don't want to just simply substitute those values with the proper ones. thanks! |
I am facing the similar problem. Did any one solved the issue?
My mesh was created using GAMBIT and it's a wedge geometry. |
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