Mesh used for Combustion Simulation

Stein · May 9, 2009, 08:45

I am doing combustion simulation these days ,and have met some problems.
Firstly,problem about mesh used for combustion.
Which kind of mesh would be better for combustion simulation?
I found that nearly all cases in CFX -help tutorial have employed tetra mesh for simulation.
So,does that means tetra would be better than hexa for CFX solver.
And I have done a few testing case ,I found that flames in results are better by using tetra than hexa mesh.
So , any friends who have experiences in combustion simulation can give me some advices.
I will appreciate very much.

ghorrocks · May 10, 2009, 21:50

Hi,

I think you will find a good quality hex mesh will always be more accurate and more stable then a tet mesh, but if your geometry is difficult to fit a quality hex mesh (as most combustors are) then you will get a better mesh from tet meshes.

Whichever way you go make sure your mesh quality is as good as you can get for combustion modelling. These models are notoriously unstable so need high quality meshes.

Glenn Horrocks

joey2007 · May 12, 2009, 17:09

Glenn is right: the tutorials meshes are compromises.

My personal experience is that TFC requires better mesh qualities than EDM. Found that also for another solver. Does anybody have experience with that? Similar findings? Reason?

Jwala.R · May 14, 2009, 06:05

Hi,
Though solution from hex mesh modelling is accurate and better but sometimes it's not possible to capture the regions of the component like combustors or afterburners.Then you go for tet mesh.

Stein · May 14, 2009, 10:58

I frequently met a problem when using EDM/FRC model.The conservation target in convergence criteria in CFX cant always be reached.
When I monitored imbalance plot in solver manager, the imbalance plot of CO component equation always presented oscillation,and cant approach to ballance.
I have tried all the methods to solve this problem ,but failed all the time .
So, is there anybody who can give some advice.I nearly lost my confidence now.
I am here deadly in need of help!

ghorrocks · May 14, 2009, 18:24

This was written for simple flows but applies also to chemistry as well:

http://www.cfd-online.com/Wiki/Ansys...gence_criteria

It is just when modelling chemistry there are a whole bunch of extra things to get right, but unless the basics discussed in the reference are under control the chemistry is never going to work.

Glenn Horrocks

May 9, 2009, 08:45	Mesh used for Combustion Simulation	#1
Stein New Member Stein Join Date: Apr 2009 Location: Shanghai in China Posts: 11 Rep Power: 17	I am doing combustion simulation these days ,and have met some problems. Firstly,problem about mesh used for combustion. Which kind of mesh would be better for combustion simulation? I found that nearly all cases in CFX -help tutorial have employed tetra mesh for simulation. So,does that means tetra would be better than hexa for CFX solver. And I have done a few testing case ,I found that flames in results are better by using tetra than hexa mesh. So , any friends who have experiences in combustion simulation can give me some advices. I will appreciate very much. Phanindra Raavi likes this.

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May 10, 2009, 21:50		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Hi, I think you will find a good quality hex mesh will always be more accurate and more stable then a tet mesh, but if your geometry is difficult to fit a quality hex mesh (as most combustors are) then you will get a better mesh from tet meshes. Whichever way you go make sure your mesh quality is as good as you can get for combustion modelling. These models are notoriously unstable so need high quality meshes. Glenn Horrocks

May 12, 2009, 17:09		#3
joey2007 Senior Member Join Date: Mar 2009 Location: Europe Posts: 169 Rep Power: 17	Glenn is right: the tutorials meshes are compromises. My personal experience is that TFC requires better mesh qualities than EDM. Found that also for another solver. Does anybody have experience with that? Similar findings? Reason?

May 14, 2009, 06:05		#4
Jwala.R New Member Jwala Join Date: May 2009 Posts: 10 Rep Power: 16	Hi, Though solution from hex mesh modelling is accurate and better but sometimes it's not possible to capture the regions of the component like combustors or afterburners.Then you go for tet mesh.

May 14, 2009, 10:58		#5
Stein New Member Stein Join Date: Apr 2009 Location: Shanghai in China Posts: 11 Rep Power: 17	I frequently met a problem when using EDM/FRC model.The conservation target in convergence criteria in CFX cant always be reached. When I monitored imbalance plot in solver manager, the imbalance plot of CO component equation always presented oscillation,and cant approach to ballance. I have tried all the methods to solve this problem ,but failed all the time . So, is there anybody who can give some advice.I nearly lost my confidence now. I am here deadly in need of help!

May 14, 2009, 18:24		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	This was written for simple flows but applies also to chemistry as well: http://www.cfd-online.com/Wiki/Ansys...gence_criteria It is just when modelling chemistry there are a whole bunch of extra things to get right, but unless the basics discussed in the reference are under control the chemistry is never going to work. Glenn Horrocks