Overset mesh error

Caterpillar85 · February 10, 2013, 13:56

Hello everyone!

I tried to simulate two boats sailing (one in front of the other) in model scale.
The goal is to catch the movements of the two boats, one on the wake of the other.
I setted up two "overset mesh" (one for each boat region) and a "tank" as fluid volume control.
I also setted up two DFBI motion to move the boats in opposite directions and to allow x,z motions (translation and sinkage) and x,y rotations (roll and trim).
The mesh generation is full achieve with about 1M cells, but when I start the computation CCM+ give this error:
"Found Inactive DonorCells in Region "Tank" . This might be due to too fine or too coarse mesh or due to an overlapping of overset regions."

I check the "Overset cell status" and I don't find any error.

Which is the possible error??

Thanks so much

ryancoe · February 10, 2013, 21:09

This is sort of the generic error for the overset mesh module. As of the current release, there's no way to figure out exactly where the mesh is deficient.

From my experience, it generally means that the mesh is too coarse where the overlap is occurring. I haven't found a good way of addressing this systematically, other than just incrementally increasing mesh density.

Good luck!

Ryan

Ps. Can you really simulate this system with only 1M cells?

lava12005 · February 12, 2013, 05:54

Hmm normally it happens for me when the higher density mesh for resolving the free surface mesh on the domain overlap with the coarser area on the overset. And eventually the interpolation doesn't work.

Try to make sure that no matter what movement you have on the overset box, the overset box always has its finer mesh intersecting with same or coarser mesh resolution on the domain mesh.

And as the error stated, make sure that the two overset meshes are not overlapping with each other.

Hope this helps.

February 10, 2013, 13:56	Overset mesh error	#1
Caterpillar85 New Member Daniele Join Date: Feb 2013 Posts: 2 Rep Power: 0	Hello everyone! I tried to simulate two boats sailing (one in front of the other) in model scale. The goal is to catch the movements of the two boats, one on the wake of the other. I setted up two "overset mesh" (one for each boat region) and a "tank" as fluid volume control. I also setted up two DFBI motion to move the boats in opposite directions and to allow x,z motions (translation and sinkage) and x,y rotations (roll and trim). The mesh generation is full achieve with about 1M cells, but when I start the computation CCM+ give this error: "Found Inactive DonorCells in Region "Tank" . This might be due to too fine or too coarse mesh or due to an overlapping of overset regions." I check the "Overset cell status" and I don't find any error. Which is the possible error?? Thanks so much

February 10, 2013, 21:09		#2
ryancoe Member Ryan Coe Join Date: Jun 2010 Location: Albuquerque, NM Posts: 98 Rep Power: 15	This is sort of the generic error for the overset mesh module. As of the current release, there's no way to figure out exactly where the mesh is deficient. From my experience, it generally means that the mesh is too coarse where the overlap is occurring. I haven't found a good way of addressing this systematically, other than just incrementally increasing mesh density. Good luck! Ryan Ps. Can you really simulate this system with only 1M cells? __________________ Ryan

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February 12, 2013, 05:54		#3
lava12005 Senior Member KHB Join Date: Aug 2010 Location: Singapore Posts: 118 Rep Power: 15	Hmm normally it happens for me when the higher density mesh for resolving the free surface mesh on the domain overlap with the coarser area on the overset. And eventually the interpolation doesn't work. Try to make sure that no matter what movement you have on the overset box, the overset box always has its finer mesh intersecting with same or coarser mesh resolution on the domain mesh. And as the error stated, make sure that the two overset meshes are not overlapping with each other. Hope this helps.