I am running a sliding mesh simulation for a wind turbine in a nozzle (i.e. a ducted turbine), but at the moment I am having the problem that my solution just blows up after a few time steps - continuity and some of the other residuals diverge and become exceedingly large. I have been running my simulation in ANSYS Fluent, but I do my CAD modeling in SolidWorks the import it over. This method worked fine for the other sliding mesh work I did.
I tried reducing my time step, and that seemed to help get to a later time, but I'm still seeing some significant instability eventually. I heard there was some way to improve the mesh matching between my rotating section and the stable section that would help fix the problem, but I haven't been able to track down how to do that.
Does anyone have advice on getting better connection between a rotating mesh and a stationary one? It seemed like it was a common problem when I was searching online, but I wasn't finding a solution to it. I'm still trying to make adjustments to get the system to work properly.
Hello Jonathan Corbett ,
in my experience you have to look out for some points in sliding mesh simulations:
1. While rotating, the two meshes should not overlap each to much other at their borders,since they not strictly circular you can not prevent it completely (FLUENT will give a warning negative volume detected if that "overlapping" becomes to much).You can more or less prevent that behaviour during meshing, if you first disable defeaturing at your interface faces and secondly choose an appropriate mesh size to resolve the circular shape of the zone interfaces.
2. You should pick you time step that each rotation is resolved with at least 50-100 timesteps.
3. The mesh sizes at the interfaces should not differ to much, to avoid larger interpolation errors.
(4. At one time, I observed that the chosen order of the interfaces too each other in the interfaces dialog had an influence on the solution, but that might be a bug in some specific version of fluent , I have not looked into that very much, since it worked by simply switching the order...)
Hello.
I will try help you, but first could you will send to my e-mail ([email protected]) your 3D trubin model, I check model and try resolve modleing.
Best Regards
Poul Lonkwic
Thank you for the offer, Poul, but I think I have resolved my problem for now.
For posterity sake, it seems my problem was that the space between my sliding mesh and the tip of my turbine blade was too small, and the mesher was not automatically making the mesh smaller to work in that space; specifically, I had set a 1 cm gap while using a 2.5 cm element maximum size. I had also defined my inflation layer such that 1 cm was not enough space to fill it out, which exacerbated the problem.
I fixed the problem by increasing the space between the blade tip and the rotating zone to 10 cm; I think there was probably a way to make the mesh much finer instead. That would have taken much longer to resolve, but I suspect it would have worked.
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