EDIT: This has been turned into a feature request since the new way of disallowing a face to be both a slip wall and a symmetry plane always results in no-slip walls on the symmetry plane, if you use a symmetry plane.
The topic posts discuss the issue.
I would like to be able to assign a face as a slip wall and a symmetry plane.
I am OK if all my symmetry planes defined by faces are automatically (and permanently) set to no-slip walls.
0voters
A few months ago I ran many incompressible external simulations where my symmetry plane was also a face of the Background Mesh Box.
Now when I try to run a new simulation in those projects I get this error:
you can simple use that face as a symmetry plane and leave the other ones as slip, that’s fine. To be safe here share the project with me (if that’s not the other one we already talked about) and I will have a look at the setup.
So in a private project I have looked a little further into this problem and I DO see a problem in that if I use the face only as a symmetry plane, the results show that there is a boundary layer on that plane which is NOT acceptable.
I am unable to post process that public project any more so I am not able to show you the above fact (which is another problem which maybe you could look at).
SO, my first post is still valid and simply using the face as a symmetry plane is not acceptable, it also needs to be a SLIP wall . EDITED (used to say no-slip here).
Why do you think that the boundary layer is not valid? Also the symmetry plane has to be a symmetry boundary condition as the name implies - a no-slip condition is zero velocity at the walls which is not the case for you I guess?!
A no-slip wall on a symmetry plane does not have sense to me. This prevents air from coming down the symmetry plane surface (or near it) at the speed it should when it hits the geometry faces at the symmetry plane.
It indeed is unphysical in your case (cannot think of one where this should be correct anyway). Also inflated boundary layers have to be added do your geometry - think you have experimented with this quite a lot before
the mesh right now looks fine except around your object in the regions perpendicular to the plane as well as the z direction. I would extend the directions and make sure the mesh fineness will be increased as I think this is too coarse at the moment, BLayer looks good and only has to be applied to the object and not the symmetry face.
Thanks for those comments but I was looking for feedback regarding the fact that I no longer use symmetry planes in my simulations, I just have a slip wall bounding box face that splits my full geometry. This project only shows the incorrect use use a symmetry plane which nowadays results in the symmetry face being a no-slip wall.
The UI now allows any bounding box face to have boundary layers created, or NOT, on them, each with different layering parameters if you use the Hex-dominant parametric meshing algorithm!
I can now use the Symmetry plane boundary condition again because external aero CFD projects should almost never need boundary layers on the faces of a bounding box.
The only time I can see the need for layers on a face of the bounding box is if the wheels of a car are contacting it or you are investigating ground effect conditions. Then you have to also be sure to do a surface refinement on that face to a cell size level that is the expansion ratio used bigger than the last layer in the boundary layer.
Does anyone else see any other projects that would need a BL generated on a bounding box face?
