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

Compressible flow problem

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

Reply
 
LinkBack Thread Tools Display Modes
Old   March 5, 2014, 00:40
Default Compressible flow problem
  #1
Senior Member
 
Bharath kumar
Join Date: Apr 2009
Posts: 157
Rep Power: 8
bharath is on a distinguished road
Hi to all,
I am simulating a compressible flow with Steam(Equilibirium) in CFX.My input BC's are,

Inlet Total Pressure = 0.05768 atm & T = 308.82 K (mass flow =111.17 kg/s)
Outlet Static Pressure = 0.05004 atm
Reference Pressure = 0 atm

Material: Steam Vapour (IAPWS table).

I started with water ideal gas and it is converged.When switching to steam it is not able start the calculation.
I tried different options and getting different warnings(Invalid number,Floating point, Over flow,High mach number,Table Clipping error and etc..)

Could anybody help me to solve this problem.

Thanks in Advance
bharath is offline   Reply With Quote

Old   March 5, 2014, 05:24
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,795
Rep Power: 84
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
IAPWS are always hard to converge.

You are using the ideal gas result as an initial condition? That will help a lot.

Also (the standard stuff for numerical instability): Improve mesh quality, double precision numerics, smaller time steps, start with low order advection (Upwinding).
ghorrocks is online now   Reply With Quote

Old   March 11, 2014, 06:03
Default
  #3
Senior Member
 
Bharath kumar
Join Date: Apr 2009
Posts: 157
Rep Power: 8
bharath is on a distinguished road
Thanks Glenn for your reply.

1) After so many trials i managed to converge 2 cases (Total 5 different Pressure BC cases & Same mesh).But other cases reporting high Mach number and solver is failing.

2) How i can deal this high mach number warning...
bharath is offline   Reply With Quote

Old   March 11, 2014, 07:21
Default
  #4
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,795
Rep Power: 84
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
As I said: Improve mesh quality, double precision numerics, smaller time steps, start with low order advection (Upwinding).
ghorrocks is online now   Reply With Quote

Reply

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
Having Problem solving 2D supersonic flow around a plug nozzle chrislloyd FLUENT 7 July 22, 2015 13:09
Problem, adding passive scalar transport for turbulent, compressible flow cryple OpenFOAM Programming & Development 2 March 25, 2013 12:00
Boundary condition for compressible flow ( cavity lid problem) pike@91 Main CFD Forum 2 June 2, 2012 17:04
Negative density problem. compressible flow Karl CD-adapco 2 July 10, 2008 16:41
Problem on boundry of two phase flow youngan CFX 0 June 30, 2003 02:32


All times are GMT -4. The time now is 22:11.