[thezack]

Hi, I am having an error in my simulations that I cannot seem to fix. I have a turbine (DFBI 1 axis rotation) rotating inside of another larger mesh. The purpose of the simulation is to simulate a gravitational vortex turbine (water enters from the top of a funnel and swirls down the funnel creating a vortex, and a turbine is placed at the bottom to rotate a shaft). The simulation is 3D. Mesh 1 is the polyhedral mesh of the funnel volume, and mesh 2 is the overset mesh of the turbine completely enclosed within mesh 1. Both are polyhedral mesh, mesh 2 has prism layer mesher, surface remesher, and surface wrapping meshing models. Mesh 1 has polyhedral, prism layer, and surface remesher.

I keep trying varying levels of mesh size for mesh 1 and mesh 2, and I keep getting this error message:


Updating indirect region interface Overset Mesh 1 between Turbine and SwirlyMarch5NoDamEntrance.
Failed to cut hole in region SwirlyMarch5NoDamEntrance.
This might be due to an overlapping of overset regions or due to invalid mesh configuration!

Am I using the wrong meshing models? Should mesh 1 or mesh 2 be finer? Should they be roughly the same mesh size or should 2 be much finer? I am new to this, and I have no idea how to proceed. I keep messing around with the mesh properties and nothing seems to work. I am not sure if there is something specific I should be changing. The documentation on Star CCM+ has a troubleshooting section, but it does not say how to fix those kinds of errors. Ive tried setting up the scalar overset mesh type scene, but of course it is in 2-D when my simulation is 3-D, so I cannot see where on the mesh the error is. I am pretty stumped here and would greatly appreciate any help. Thanks!

[ryancoe]

Zack,

The overset mesh can be challenging to configure. I've had some luck using a series of plane sections with the Overset Scalars to try to find the locations where you're having problems. Its a bit unwieldy, but its the best thing I've found thus far.

If that doesn't help, I would try to simplify the geometry to make it more overset-friendly until you get it working, and then work back to full fidelity.

[hyderkhan74]

Hi
I have the same problem so i wonder how you solve it ?
thanks in advance

[ayannath23]

Hi Zack,
I think the error is due to improper mesh..
Please go through the tutorial in star ccm+ help (Tutorial Guide > Motion > DFBI: Lifeboat with Overset Mesh). It explains nicely about the meshing requirements.

Thanks,
Ayan

[Kush7876]

Proper meshing would solve this problem, you should make sure that there should at least 3 cells of overset mesh are there on 1 cell of background mesh and also you should maintain the same through out the path in which overset mesh is travelling.

Further please refer to "best practices for overset mesh" in star user guide

[Dan709]

Originally Posted by Kush7876

Proper meshing would solve this problem, you should make sure that there should at least 3 cells of overset mesh are there on 1 cell of background mesh and also you should maintain the same through out the path in which overset mesh is travelling.

Hi Kush,

Are you saying that in the overlap region between the overset and background meshes, the overset cell size should be 1/3 of that of the background mesh? To get the three overset cells inside one background cell like you mentioned. Is this just from your personal experience or did you find it documented somewhere?

Thanks!
Dan

[Kush7876]

Dan,

It's from the experience. It worked if 1cell of background mesh have more than 3 cells of overset mesh.

[EDE16]

Zack,

I have caried out windturbine simulations with the rotating mesh option (Rigid Body Motion) its works easily and results were very good.