rotating mesh with cyclic boundaries
 

Hello everybody,

first of all i have to admit, that this is my first bigger project with OpenFoam. I wish to simulate a radial compressor stage using rhoPimpleDyMFoam. In order to get a quick solution i would like to use cyclic patches and rotate the whole mesh with a constant rotational speed between an inlet- and outlet-mesh. So, my question is simple : Is it possible to use cyclic patches instead of meshing the whole stage in this case?
For example: would it be possible to change the tutorial " annularThermalMixer " that way, so that there is just one single blade and a piece of the outer mesh?
I would be very happy, if someone could help me with this question. I already read some stuff about GGI and dynamic Meshes, but until now i didnt found a solution :(

Thanks for support.

fixed Wall
 

OK, I solved the problem by editing an "dynamicMeshDict" -file.Now my mesh rotates, as it should :D. But now I have a new problem: the upper wall have to stand still. I think that would be no problem, if there is a big gap between the shovel and the channel-wall (like in the annularThermalMixer-case), but in this case the gap is around 0,5 mm thin. So there are just a few number of cells in it. I dont exactly now how the tutorial "annularThermalMixer" work, but in my oppinion it would be the simplest way to do it similar. But I have a little doubt of it, because its so near to the wall and may disturb the solution of the boundary-layer. Does anybody now a more simple way???Is it possible for example to write a boundarycondition in the manner U_w=-Omega*R(z), where the velocity at the wall is negative to the direction of the rotation but not constant in place?

Thanks for help and best regards!

Hi Chrisitan,

you could choose the BC "rotatingWallVelocity".

Regards

Thomas

thx
 

Hi Thomas!
Thank you very much for your reply!
Wouldnt be me, if there would be no more question at this point :D :
Is rotatingWallVelocity-BC at the Rotor on static mesh the same like a moving mesh with uniformValue (0 0 0) -BC on the Rotor?

Best Regards,

Christian!

Hi Christian,

for simulating moving mesh, I define the moving regions within the rotating mesh with the BC "movingWallVelocity" (value is set to uniform (0 0 0)). For rotating faces within the non-rotating mesh, I set the BC "rotatingWallVelocity".

Regards

Thomas

Haudi Thomas!
Thanks for your answer!
I have tried for innerwall AND blade (rotor) the following (non-moving mesh) for U:

type rotatingWallVelocity;
origin (0 0 0);
omega 100;
value uniform (0 0 0);

and the outerwall

type fixedValue;
value uniform(0 0 0);

The strange thing is, that, when I plot the solution, the velocity at the innerwall is , as expected not 0, but on the blade it is 0... how is that possible? there must be something wrong...
Im also running the dynamic-mesh case, which seems to do a better job.
I'll post my results as I get them.

Best Regards,

Christian.