CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > CFX

Turbulence Model Solver Fail

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   September 6, 2018, 04:18
Default Turbulence Model Solver Fail
  #1
Senior Member
 
Pedro Oliveira
Join Date: Feb 2018
Location: Portugal
Posts: 109
Rep Power: 8
oliveira1820 is on a distinguished road
My simulation consists of a Multiphase simulation where the heated recepient is cooled by surrounding water flow in a channel.

In the recipient I have water vapour and liquid water with buyoancy, turbulence, Total energy, particle and thermal phase change model.


In the cooling water domain I have buyoancy model, Total energy model and when I consider the flow of cooling water laminar the solver runs normally, but when I add the Turbulence model it fails in the first iteration at the 4th coeefficient loop.

I have an optimized mesh ( with good skewness and small elements) and small iteration steps time(1*10-5 s).

The solver fails when I activate the the turbulence model on the cooling water. What can I do to make the solver work?
oliveira1820 is offline   Reply With Quote

Old   September 6, 2018, 06:17
Default
  #2
Senior Member
 
Gert-Jan
Join Date: Oct 2012
Location: Europe
Posts: 1,928
Rep Power: 28
Gert-Jan will become famous soon enough
It can be anything. Please share your output files (the laminar case and the crashing turbulent case) so we can take a closer look.
And maybe a picture of your case..........
Gert-Jan is offline   Reply With Quote

Old   September 6, 2018, 16:33
Default
  #3
Senior Member
 
Pedro Oliveira
Join Date: Feb 2018
Location: Portugal
Posts: 109
Rep Power: 8
oliveira1820 is on a distinguished road
Here it is the OUT file when crashes
Attached Files
File Type: txt Out file.txt (92.5 KB, 3 views)
oliveira1820 is offline   Reply With Quote

Old   September 6, 2018, 21:48
Default
  #4
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,871
Rep Power: 144
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
FAQ: https://www.cfd-online.com/Wiki/Ansy...do_about_it.3F
__________________
Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.
ghorrocks is offline   Reply With Quote

Old   September 7, 2018, 14:28
Default
  #5
Senior Member
 
Join Date: Jun 2009
Posts: 1,880
Rep Power: 33
Opaque will become famous soon enough
This type of problem is best to build one step at a time.

1- You are using a beta feature not fully tested; therefore, be prepared.

2- Go single phase on both sides first, so the basics are easier and checked out

3- Introduce multiphase with the previous single phase being the dominant phase, or alternatively, remove the interphase interaction (be sure the setup is consistent) and set both a 50% volume fraction. Both phases should behave the same as single phase, then slowly moves towards your goal.
Opaque is offline   Reply With Quote

Old   September 9, 2018, 09:57
Default
  #6
Senior Member
 
Gert-Jan
Join Date: Oct 2012
Location: Europe
Posts: 1,928
Rep Power: 28
Gert-Jan will become famous soon enough
Pedro,

you are trying so solve a very difficult physical problem. In CFX-Pre, you turn on all physical models, and let the CFX-solver find out for himself, while keeping fingers crossed. That is not how it is going to work.

As Opaque mentioned, start as simple as possible (start with plain air through your system) and if the results are fine, increase complexity. Do it step by step.

Some specific help
- show me your dimensional analysis where you prove gravity is an important phenomena to include.
- Why do you run transient? Why not steady state?
- if you want to run transient, then why not use your 'converged' laminar solution as an initial guess?
- you have an inlet and an outlet, both with massflow sepcified 2.2kg/s. Why don't you use a pressure boundary? That is much more logical.
Gert-Jan is offline   Reply With Quote

Reply


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 Centurion2011 FLUENT 48 June 15, 2022 00:29
In the case of convergence aja1345 FLUENT 1 July 31, 2015 04:58
Force can not converge colopolo CFX 13 October 4, 2011 23:03
Convergence of CFX field in FSI analysis nasdak CFX 2 June 29, 2009 02:17
Defect correction and convergence ganesh Main CFD Forum 4 June 30, 2006 15:20


All times are GMT -4. The time now is 01:13.