[JohnAB]

Hello,

I want to simulate an object moving in a channel where the walls would be close to the object.
I know I can do that with a moving mesh, but since I want to save computation time and cells, I thought I could just have a short section of the channel, my fixed object inside it, and have the air flowing through.
The thing is, here the walls are pretty close to the object and I end up with this issue:
- in the real application where it is the object that is moving in the channel, the air is static and does not moved with respect to the walls. In my new setup, the air is moving with respect to those walls.
- I believe that simply putting a "slip" condition on the walls does not have the same effect. Is using the "tangential velocity specification" and adding a vector corresponding to the velocity of the air the thing to do ?

Unfortunately, I cannot run the moving mesh to compare and make sure I have the right setup in my "fixed frame" simulation...

thanks for your help!

[fluid23]

Sounds like you are on the right track. No slip is for a 'frictionless' surface, you have friction. Your surface is moving, aka a moving wall. I have never used it, but from the help documentation it sounds like tengential velocity specification is what you want.

[ggulgulia]

Hi

if increasing in computation time is what you are afraid of in your case, you can do an initial study of comparison by using tangential velocity-fixed frame and no slip velocity-moving reference frame (maybe a cylinder in a pipe) and see how the results compare. This will give you a fair idea of the trade-off you will be in for.

[JohnAB]

thank you guys,

I am comparing the "fixed mesh" simulation using the tangential velocity boundary and the moving-mesh that I was able to cut short enough so that I can make it run with an acceptable mesh, will see what the results give!