|
[Sponsors] |
Question about coarsening the mesh to improve convergence |
|
LinkBack | Thread Tools | Search this Thread | Display Modes |
August 10, 2012, 16:43 |
Question about coarsening the mesh to improve convergence
|
#1 |
Senior Member
Meimei Wang
Join Date: Jul 2012
Posts: 494
Rep Power: 15 |
Hi
I have vortex at some domains of my case. The FAQ suggests me to coarsen the mesh to improve the convergence. But that will decrease the accuracy. Is there any other ways to improve the convergence for this problem?
__________________
Best regards, Meimei |
|
August 10, 2012, 23:56 |
|
#2 |
New Member
Sainath
Join Date: Mar 2012
Posts: 27
Rep Power: 14 |
Only way you are going to capture vortices is through a fine mesh. Let me know what you are trying to model. Let me see if i can helpyou out
|
|
August 11, 2012, 05:40 |
|
#3 |
Senior Member
Meimei Wang
Join Date: Jul 2012
Posts: 494
Rep Power: 15 |
Sorry, I'm not allowed to reveal that geometry. But do you mean that I can solve this problem by refining the mesh and match the mesh with the fluid behavior?
__________________
Best regards, Meimei |
|
August 11, 2012, 06:31 |
|
#4 |
New Member
Sainath
Join Date: Mar 2012
Posts: 27
Rep Power: 14 |
If you are planning to capture vortex formation and shedding you need to have a fine mesh such that it is captured. Very small eddies can also be captured using sub grid scale type of modeling.
But there are constraints like you need to have a good computational power. Using a LES or DES model is going to be computational intensive. So plan accordingly. O If your aim is something else and vortices are formed just as the side effects of the problem then you can refine the mesh only in those are and can go in with a coarse mesh in the other areas. I really do not know what your problem is, these are just requirements for capturing vortices. Also go through the FAQ's, you may find some more tips to find effective convergence and accuracy. |
|
August 12, 2012, 01:56 |
|
#5 |
New Member
Join Date: Oct 2011
Posts: 20
Rep Power: 14 |
It isnt always required for your residual to converge. If capturing vortex is not important then you can use monitor plots like mass flow, pressure to see if you have achieved fair enough convergence.
|
|
August 12, 2012, 08:03 |
|
#6 | |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,703
Rep Power: 143 |
Quote:
|
||
August 12, 2012, 13:25 |
|
#7 |
Senior Member
Meimei Wang
Join Date: Jul 2012
Posts: 494
Rep Power: 15 |
I only care about the pressure drop. I don't care about the vortex at all. But I'm wondering if I don't solve the vortex, could the simulation pressure drop results still be accurate?
__________________
Best regards, Meimei |
|
August 12, 2012, 13:30 |
|
#8 | |
Senior Member
Meimei Wang
Join Date: Jul 2012
Posts: 494
Rep Power: 15 |
Quote:
A physical instability, such as vortex shedding - the fix here is to use a larger timescale, a coarser mesh in the vortex shedding region, decrease the blend factor (if using hybrid differencing) or use a lower order turbulence model. The first option is preferred as the latter options can have accuracy implications. ' It's from the FAQ of this forum.
__________________
Best regards, Meimei |
||
August 12, 2012, 21:57 |
|
#9 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,703
Rep Power: 143 |
I wrote the FAQ so if it is unclear I would like to improve it.
My intention was to say that if the vortex is not important in the flow for the results you are interested in then you can dissipate out the vortex by coarsening that region of the mesh. But if this is an important part of the flow - for instance it adds resistance which significantly contributes to the over pressure drop in the simulation - then it is important and you should not get rid of it. So before you coarsen that region of mesh you have to make sure that it is not significantly contributing to important flow features. Only if it is not then you can coarsen the mesh in that area to get rid of it. |
|
August 13, 2012, 14:53 |
|
#10 |
Member
Felipe Gobbi
Join Date: Apr 2012
Location: Brazil
Posts: 76
Rep Power: 14 |
What is your problem message? What error does CFX-Solver point?
|
|
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
[ICEM] surface mesh merging problem | everest | ANSYS Meshing & Geometry | 44 | April 14, 2016 06:41 |
[ICEM] issue occur after extrude 2D airfoil mesh and convergence problem in CFX | shiyun | ANSYS Meshing & Geometry | 4 | May 9, 2012 19:55 |
A question on adaptive remeshing or mesh deformation for handling object motions | daveatstyacht | OpenFOAM | 10 | November 13, 2010 09:29 |
[snappyHexMesh] external flow with snappyHexMesh | chelvistero | OpenFOAM Meshing & Mesh Conversion | 11 | January 15, 2010 19:43 |
fluent add additional zones for the mesh file | SSL | FLUENT | 2 | January 26, 2008 11:55 |