# Problem with Convergence

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

 December 8, 2012, 08:10 Problem with Convergence #1 Member   anonymous Join Date: Dec 2012 Posts: 33 Rep Power: 6 I am having a problem with my Starccm simulation in that it will not converge to a final solution. the residuals are very high are the solution never seems to reach a steady state where everything is constant it just keeps moving. I am simulating a turbine blade and I am using the following models: gamma ReTheta K-omega Steady Turbulent 2D Coupled All Y+ treatment Ideal Gas I am hoping that there is something I can do in order to make it converge and reach a solution. I have attached some pictures so that you can tell what I mean. The solution is periodic which explains a little better the scaler plot. thanks broke_Scalar Scene 1.png broke_Residuals.png

December 11, 2012, 19:08
#2
New Member

Luís Ferrari
Join Date: May 2012
Posts: 1
Rep Power: 0
Oi, tente diminuir o fator de sobre-relaxamento, o default é 0.9, tente abaixar para 0.5, isto poderá deixar problemas de tempo em sua simulação, caso não, pode ser problema de modelo mesmo, tente colocar uma sonda e monitorar por isto.

Quote:
 Originally Posted by badger1 I am having a problem with my Starccm simulation in that it will not converge to a final solution. the residuals are very high are the solution never seems to reach a steady state where everything is constant it just keeps moving. I am simulating a turbine blade and I am using the following models: gamma ReTheta K-omega Steady Turbulent 2D Coupled All Y+ treatment Ideal Gas I am hoping that there is something I can do in order to make it converge and reach a solution. I have attached some pictures so that you can tell what I mean. The solution is periodic which explains a little better the scaler plot. thanks Attachment 17510 Attachment 17511

 December 13, 2012, 04:09 #3 Senior Member     siamak rahimi ardkapan Join Date: Jul 2010 Location: Copenhagen, Denmark Posts: 218 Rep Power: 11 Seems to me that the mesh is coarse. But before that try to change physics models from second order to first order. See if it gets converged or not. if yes, then change to second order after for example 2000 iterations. __________________ Good luck Siamak

 December 18, 2012, 05:54 #4 Member   anonymous Join Date: Dec 2012 Posts: 33 Rep Power: 6 I tried to change both the order from 2nd to 1st and also the couant number and also the relaxation. The simulation converges fine if you use segregated and constant density, but if you use coupled and ideal gas it does not and gives stupid results and never reaches a steady state solution. I need to use coupled and ideal gas to match an experiment that someone else has done.

 December 20, 2012, 14:23 #5 Senior Member     siamak rahimi ardkapan Join Date: Jul 2010 Location: Copenhagen, Denmark Posts: 218 Rep Power: 11 I think if you want to try coupled, you need to reduce more the relaxatoin factor. It will take certaily longer to converge, you need to be patient. __________________ Good luck Siamak

 Thread Tools Display Modes Linear Mode

 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 OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post Forrest_Lei OpenFOAM 3 July 19, 2011 06:00 commonyue Main CFD Forum 1 December 1, 2009 04:54 nasdak CFX 2 June 29, 2009 01:17 Emily FLUENT 2 March 21, 2007 23:18 Balraj Main CFD Forum 3 December 9, 2004 01:24

All times are GMT -4. The time now is 22:18.