CFD Online Logo CFD Online URL
Home > Forums > Main CFD Forum

Continuity Convergence problem

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

Like Tree1Likes
  • 1 Post By wxmoore

LinkBack Thread Tools Display Modes
Old   January 16, 2013, 10:57
Default Continuity Convergence problem
New Member
Join Date: Dec 2011
Posts: 29
Rep Power: 8
crispysalt is on a distinguished road

If all my residuals converge except continuity what can I do to make it converge?

crispysalt is offline   Reply With Quote

Old   January 16, 2013, 13:46
Default Continuity Convergence Problem
New Member
william moore
Join Date: Jan 2013
Posts: 8
Rep Power: 7
wxmoore is on a distinguished road
Check your overall mass balance between the inlets and outlets of the flow domain, the net mass imbalnce should be below about 0.5%. Also check mesh quality to verify it is within recommended software code guidelines for skewness, orthogonality etc. and that you have sufficient mesh resolution especially in areas of high gradients. If you are using enhanced wall treatment and k-omega SST then make sure you have enough inflation layers and the y+ value is near 1. Also try using the coupled solver instead of segregated solver and try switching to second order discretization. Also it may take more iterations before momentum equation begins to converge. As a last resort lower momentum under-relaxation and allow to run for several hundred more iterations. Finally there may be transient flow features that the steady state method cannot resolve, requiring a non steady solution method for convergence.

Good Luck,
liuch likes this.
wxmoore is offline   Reply With Quote

Old   January 28, 2013, 04:16
New Member
Join Date: Dec 2011
Posts: 29
Rep Power: 8
crispysalt is on a distinguished road
I am simulating a fluidized bed reactor using Eulerian multiphase model, I set two phases in my simulation: solid and liquid. I did patch the initial volume fraction before running. I am currently trying out the laminar flow in transient simulation first. For the boundary condition i set inlet as velocity inlet and outlet as pressure outlet with gauge pressure = 0pa. When i try to calculate, the solution is unable to converge under steady state or transient state. I tried reducing the under-relaxation factors to 0.2 ,reduce the time step and solve using the first order solution method but it still diverge. Are there other ways to make it converge?
crispysalt is offline   Reply With Quote

Old   January 28, 2013, 16:54
New Member
Simon Hubbard
Join Date: Mar 2009
Posts: 10
Rep Power: 10
monkeytron is on a distinguished road
Have you checked your maximum velocity in your domain to see if it is within expected limits? Often low mesh quality can cause high velocities which can be looked for and can show you where you might need to improve mesh quality.
monkeytron is offline   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
Convergence Centurion2011 FLUENT 44 June 20, 2017 09:57
[ICEM] issue occur after extrude 2D airfoil mesh and convergence problem in CFX shiyun ANSYS Meshing & Geometry 4 May 9, 2012 19:55
Need URGENT HELP for convergence problem of a turbine Pursuor CFX 5 October 3, 2011 17:44
CM+5 Convergence of the nonstationary problem ILYA87 STAR-CCM+ 0 May 22, 2011 04:35
Convergence problem for P1 & Energy HP FLUENT 5 May 21, 2005 15:01

All times are GMT -4. The time now is 09:51.