CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > General Forums > Main CFD Forum

convergence problem with SIMPLER

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   February 24, 1999, 07:50
Default convergence problem with SIMPLER
  #1
NURAY KAYAKOL
Guest
 
Posts: n/a
I have the following convergence problem related to SIMPLER algorithm.

suppose that you have two independent run with two different convegence solution. Say -3% and -9% energy imbalance. the definition of convergence: (heat input-heat output)/heat input/100 = x % convergence Actually x value can be minus or plus depending on the nature of theproblem. How can you compare the results of two run? For this type of iteratif solutions it is possible to stop the run with nearly 0% convergence. But at this point the variation of variables are not stable and their values change until the convergence becomes say -9% where temperature, velocity etc. remain as it is.

The main problem is this? at what point should i compare the results of a CFD code which uses SIMPLER algorithm?

Thank you for your time and interest

Best Regards

Dr. Nuray Kayakol
  Reply With Quote

Old   February 24, 1999, 13:43
Default Re: convergence problem with SIMPLER
  #2
John C. Chien
Guest
 
Posts: n/a
(1). since you did not want to impose the overall energy balance on the calculation ( because of the negative impact on the convergence of the flow variables ), the best way to make the comparison is to wait until you have converged solutions. (2). Then the energy imbalance problem can be interpreted as the uncertainty of your calculations. It may not have a linear impact on the flow field solution because the energy imbalance is an integral ( global) quantity. (3) mesh refinement may be the simplest way to reduce this uncertainty (or accuracy). (4). The related issue is the overall mass conservation. If the converged results are sensitive to the energy imbalance, then apparently it is going to be hard to make a meaningful comparison. The fact is the energy imbalance must also reach a converged state when the solutions converge. In this way, both the energy imbalance parameter and the rest of the flow variables are all in a converged state.
  Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
convergence problem when use pisoFoam, LES for wind tunnel case Forrest_Lei OpenFOAM 3 July 19, 2011 06:00
convergence problem commonyue Main CFD Forum 1 December 1, 2009 03:54
Convergence of CFX field in FSI analysis nasdak CFX 2 June 29, 2009 01:17
convergence problem in comsol anderson COMSOL 0 February 24, 2008 16:54
3D Fluid Flow Convergence problem Emily FLUENT 2 March 21, 2007 22:18


All times are GMT -4. The time now is 22:04.