# convergence issues

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

 April 2, 2010, 05:24 convergence issues #1 New Member   Francis Join Date: Apr 2010 Posts: 13 Rep Power: 9 hi im actually working on a simple flow case ( im a beginner), a cylender obstacle. im trying to hav von karman streets but first i would like to converge my calculation in steady. i had difficulties to hav it converged...i tried to change under relaxation factors, AMG post sweeps...nothing changed please help me

 April 2, 2010, 06:25 #2 New Member   zhwan Join Date: Oct 2009 Posts: 4 Rep Power: 10 Try set Reynolds Number lower. Generally, if the Re < 47, you will get a converged solution.

 April 2, 2010, 07:32 #3 Senior Member   Hamid Zoka Join Date: Nov 2009 Posts: 212 Rep Power: 11 Dear Francis; is the flow turbulent or laminar? please note that if you are to solve a flow field without using any turbulent model, you should be sure that your flow is totally laminar. if you use ordinary form of navier-stokes equations for a turbulent flow your solution will not converge. firstly check your code with laminar regime. then, if you like to switch to turbulent flow, you should know how to apply turbulent models to navier-stokes equations. regards

 April 2, 2010, 08:21 #4 New Member   Francis Join Date: Apr 2010 Posts: 13 Rep Power: 9 Re is 70 000. n i use kw sst turbulence model

 April 2, 2010, 08:23 #5 New Member   Francis Join Date: Apr 2010 Posts: 13 Rep Power: 9 thx for answering again

 April 2, 2010, 08:53 #6 New Member   zhwan Join Date: Oct 2009 Posts: 4 Rep Power: 10 hi, As i know,many people want to get converged solution for analyzing the flow stability. The flow is unsteady at a high Re. For a 2D cylinder, the transition Re is about 47, Re~180 for 3D. u can use a unsteady solver such as explicit time -marching scheme for the problem.

 April 2, 2010, 10:07 #7 New Member   Francis Join Date: Apr 2010 Posts: 13 Rep Power: 9 the tke is not converging.... zhwan im doing a specific calculation i hav to converge befor moving to unsteady please help me!

 April 4, 2010, 09:21 #8 New Member   zhwan Join Date: Oct 2009 Posts: 4 Rep Power: 10 hugocis, which method you currently use, Newton's iteration(GMRES) ? you can try to change the solver such as RPM ( Recursive Projection Method) .This method can be applied to both steady-state or unsteady caculations. The following is a thesis about RPM ------------ [PhD Thesis]Aspects of the RPM applied to flow solver. Author: Jokim Moller.

 April 6, 2010, 03:35 #9 New Member   Francis Join Date: Apr 2010 Posts: 13 Rep Power: 9 ok but i dont even know wat u talkin about im usin gauss seidel , AMG solver if that help....

 April 6, 2010, 03:43 #10 New Member   Francis Join Date: Apr 2010 Posts: 13 Rep Power: 9 now i have turbulen viscosity limited in 570 cells in ...

 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

All times are GMT -4. The time now is 06:44.