CFD Online Logo CFD Online URL
Home > Forums > CFX

solver is not converging

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

LinkBack Thread Tools Display Modes
Old   March 13, 2006, 16:35
Default solver is not converging
Vijesh Joshi
Posts: n/a
My name is Vijesh Joshi. I am a student in karnataka (India) doing my M.Tech in SDM engineering college-Dharwad. I am trying to reduce the drag by the spike attachment for a 120deg blunt cone nose. I was inspired and motivated by going through your doctorate thesis. I am going wrong somewhere by which the solver is not converging. Below I have written the geometry details, PRE-settings and solver control settings which I had kept for my problem.

Geometry details

L(spike length) = 200 mm

D(model base dia) = 300 mm

at the tip of the spike, an aerodisc of 40mm radius is being attached.

PRE settings

1. fluid domain - air ideal gas, reference pressure= 1 Pa, Laminar flow and other parameters not changed.

2. inlet - Supersonic, M2=644 m/sec, static pre=0.5643 atm, static temp = 258.3 K and others not changed.

3. Outlet - supersonic.

Solver settings

Equations - all were set to upwind scheme.

time scale - local time scale factor=0.9

residual = 1e-4 = 0.0001

  Reply With Quote

Old   March 13, 2006, 19:42
Default Re: solver is not converging
Posts: n/a
Try using the shear stress transportation model for turbulence.iam not sure why you are using the laminar flow.At super sonic speed i would presume the air to be turbulent.

Change the solver settings to high resolution.upwind is more robust and can be used for intial set of results but for accurate final one use the high resolution.

Change the reference pressure to Zero.

Set your time scale to auto and if you monitor the equations and if it is converging then change the settings while the solver is runnin using the edit form and change to physical time scale.

When it is starting to solve it will give you the auto time scale.use that to set the physical time scale to get a faster convergence.

Hope these are helpful

Thanks Regards Rajit
  Reply With Quote

Old   March 13, 2006, 23:33
Default Re: solver is not converging
Posts: n/a
What do you mean by "not converging"? Is the residual plot showed a diverging behaviour or is it just not reaching the target residual?

Is there a reason why you apply laminar flow assumption for such high Reynolds no? I'm not sure about the physics of your flow structures but you must make sure that the condition that you applied is realistic.
  Reply With Quote

Old   March 18, 2006, 10:08
Default Re: solver is not converging
Posts: n/a
how about your meshing?
  Reply With Quote


Thread Tools
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 On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
A New Solver for Supersonic Combustion nakul OpenFOAM 7 January 3, 2017 10:25
A New Solver for Supersonic Combustion nakul OpenFOAM Announcements from Other Sources 18 February 19, 2013 08:48
Quarter Burner mesh with periosic condition SamCanuck FLUENT 2 August 31, 2011 11:34
Working directory via command line Luiz CFX 4 March 6, 2011 21:02
why the solver reject it? Anyone with experience? bearcat CFX 6 April 28, 2008 14:08

All times are GMT -4. The time now is 09:06.