Overset or mesh morphing for in cylinder

MachZero · June 10, 2019, 21:42

Hello, I am creating a model of a pump that is very similar to a IC engine piston. I am struggling to figure out the best way to make this model within CCM+. I can think of good ways for fluent and some other tools but not CCM+.

With mesh morphing the mesh will likely get way too distorted over such a large stroke.

That leaves overset as the other option. Overset seems to be designed such that one object can move inside a larger domain. I haven't come across any examples where overset is used to move or shift the outer boundary. Has anyone seen anything like this or done so successfully? I've run into some problems with my setup.

steve lee · June 11, 2019, 01:26

Hi, you can find overset tutorial using help key.
the pros of overset is can simulate without remeshing
(sure closed domain is possible but it is not in this case.)

but the cons is too heavy than morphing method.

if your moving part is plat surface, try to use morphing method
if morphing boundary is outer wall, it will act like remove cells.

MachZero · June 11, 2019, 09:18

Thanks for your response. I've looked through and don't the tutorial problems, they don't seem to address this.

The problem is the domain changes in size dramatically and so performing a mesh morphing would result in very bad quality, high aspect ratio cells. Remeshing only areas of interest doesn't seem to be something that is really solidly in the workflow for CCM.

Therefore overset seems to be the only option really. Do you agree?

Could ccm simply not perform these kinds of simulations before overset?

steve lee · June 11, 2019, 21:17

I can't judge which method is better for your prblem.
Can you share the domain and more information?

Morphing and remeshing method is faster than overset usually, but the problem is that method cause some numerical noise after remeshing.
If you study to solve that problem experience, you can get much know-how to deal with the noise problem. (modeling know-how, remeshing timing, using low pass filter, etc..)

Overset method is more heavy and.. captured cells have a ideal aspect ratio. but outer boundary line of captured cell will have so many stairs if your boundary is not plat surface.

You should find which solution is better.

If you choose morphing method you have to get much know-how to use that.
In CCM+, it is very important you use region base or part base because there are some different way to use morphing method.

I hope you find good process for your work

June 10, 2019, 21:42	Overset or mesh morphing for in cylinder	#1
MachZero Member Join Date: Aug 2011 Posts: 89 Rep Power: 14	Hello, I am creating a model of a pump that is very similar to a IC engine piston. I am struggling to figure out the best way to make this model within CCM+. I can think of good ways for fluent and some other tools but not CCM+. With mesh morphing the mesh will likely get way too distorted over such a large stroke. That leaves overset as the other option. Overset seems to be designed such that one object can move inside a larger domain. I haven't come across any examples where overset is used to move or shift the outer boundary. Has anyone seen anything like this or done so successfully? I've run into some problems with my setup.

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June 11, 2019, 01:26		#2
steve lee Member Steve Join Date: Mar 2018 Location: South Korea Posts: 69 Rep Power: 8	Hi, you can find overset tutorial using help key. the pros of overset is can simulate without remeshing (sure closed domain is possible but it is not in this case.) but the cons is too heavy than morphing method. if your moving part is plat surface, try to use morphing method if morphing boundary is outer wall, it will act like remove cells.

June 11, 2019, 09:18		#3
MachZero Member Join Date: Aug 2011 Posts: 89 Rep Power: 14	Thanks for your response. I've looked through and don't the tutorial problems, they don't seem to address this. The problem is the domain changes in size dramatically and so performing a mesh morphing would result in very bad quality, high aspect ratio cells. Remeshing only areas of interest doesn't seem to be something that is really solidly in the workflow for CCM. Therefore overset seems to be the only option really. Do you agree? Could ccm simply not perform these kinds of simulations before overset?

June 11, 2019, 21:17		#4
steve lee Member Steve Join Date: Mar 2018 Location: South Korea Posts: 69 Rep Power: 8	I can't judge which method is better for your prblem. Can you share the domain and more information? Morphing and remeshing method is faster than overset usually, but the problem is that method cause some numerical noise after remeshing. If you study to solve that problem experience, you can get much know-how to deal with the noise problem. (modeling know-how, remeshing timing, using low pass filter, etc..) Overset method is more heavy and.. captured cells have a ideal aspect ratio. but outer boundary line of captured cell will have so many stairs if your boundary is not plat surface. You should find which solution is better. If you choose morphing method you have to get much know-how to use that. In CCM+, it is very important you use region base or part base because there are some different way to use morphing method. I hope you find good process for your work