|
[Sponsors] |
higher grid resolution --> later convergence? |
|
LinkBack | Thread Tools | Search this Thread | Display Modes |
October 31, 2013, 06:35 |
higher grid resolution --> later convergence?
|
#1 |
New Member
Udo
Join Date: Oct 2013
Location: Munich
Posts: 3
Rep Power: 12 |
Hello,
I'm new here and in the CFD-World. At the moment I'm writing my bachelor's thesis about a fluid flow problem. My question: Can anybody give a brief explanation about the fact, that if you calculate the same case for different meshes (for a grid study) it needs more iterations to converge the higher the grid resolution respectively the cell number is? Thank you very much in advance! |
|
October 31, 2013, 07:33 |
|
#2 | |
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,760
Rep Power: 71 |
Quote:
your question is not very clear... convergence in what? What kind of formulation and solver are you using and for solving what? What about your starting vector? Just speaking in general, if you solve a linear system with an interative method, the rate of convergence of the method depends on the spectral radius of the iteration matrix. Thus, while changing h, you should check if the spectral radius changes. |
||
October 31, 2013, 09:43 |
|
#3 |
New Member
Udo
Join Date: Oct 2013
Location: Munich
Posts: 3
Rep Power: 12 |
Excuse me for not expressing clearly and thanks for your answer!
Im not deep into theoretical backgrounds yet. And my advisor at the university is neither. I have three grids for a combustion furnace with inlet and outlet. Im using FLUENT with steady-state flow and pressure-based solver (SIMPLE). The residuals of the coarsest grid are converging earlier than they're doing with finer meshes. What is the reason? Why doest it need not only a longer computing time, but also more iterations till the flow is fully developed? I'm kindly asking for a quite simply answer, if there is one. I hope I made myself sufficiently clear enough. Thank you in advance. |
|
October 31, 2013, 09:46 |
|
#4 | |
Senior Member
Join Date: May 2012
Posts: 544
Rep Power: 15 |
Quote:
|
||
October 31, 2013, 10:47 |
|
#5 |
New Member
Udo
Join Date: Oct 2013
Location: Munich
Posts: 3
Rep Power: 12 |
Thanks. That sounds plausible ;-)
|
|
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Problem with Grid convergence study | dialolema | CFX | 1 | June 14, 2010 19:33 |
Grid resolution - Segmentation fault | George | Main CFD Forum | 0 | September 4, 2007 18:38 |
Large difference in grid resolution for diff paper | Ben | Main CFD Forum | 16 | April 7, 2007 12:45 |
Higher order discretization on staggered grid | Chandra Shekhar | Main CFD Forum | 9 | January 27, 2005 17:31 |
ratio grid resolution (near wall/center) of dispersed bubbly flow columns using LES | Ridwan Setiadi Arrizar | Main CFD Forum | 1 | January 30, 1999 18:43 |