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

Resolving for one extra variable?

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   December 7, 2008, 08:49
Default Resolving for one extra variable?
  #1
Matt
Guest
 
Posts: n/a
Hi,

I've completed numerous runs and realised that I did not have density being output as a selected variable. This means that I cannot calculate the massflow for the affected timesteps.

Is there a simple or quick way, without re-solving each run, to make CFX calculate the density for each run?

Kind Regards, Matt.
  Reply With Quote

Old   December 7, 2008, 18:06
Default Re: Resolving for one extra variable?
  #2
Glenn Horrocks
Guest
 
Posts: n/a
Hi,

If the simulations are incompressible then density is constant so you can work out the volume flows and convert to massflows easily.

If the flow is compressible - well you need to have two independant gas properties to define the gas state. From any two properties you can calculate any other property. If you don't have two properties then your only choice is to re-run the simulation.

Glenn Horrocks
  Reply With Quote

Old   December 7, 2008, 21:05
Default Re: Resolving for one extra variable?
  #3
Matt
Guest
 
Posts: n/a
Thanks for the quick response Glenn.

I did export Pressure and Velocity, but without temperature I don't think I can calculate out the density.

Looks like I'll have to re-run some of the solutions.

Cheers, Matt.
  Reply With Quote

Old   December 8, 2008, 18:02
Default Re: Resolving for one extra variable?
  #4
Glenn Horrocks
Guest
 
Posts: n/a
Hi,

I think you have mis-understood me. If you are using an idal compressible gas you only need two parameters to define the state of the gas. State variables are temperature, pressure, density, enthalpy, entropy. If you have any two of these variables you can calculate any others. Velocity is not a state variable, but if you have total pressure, static pressure and velocity you will be able to get the density.

But if you only exported pressure and velocity and it is a compressible simulation then your only choice is to rerun to get density.

Glenn Horrocks
  Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
emag beta feature: charge density charlotte CFX 4 March 22, 2011 10:14
error in COMSOL:'ERROR:6164 Duplicate Variable' bhushas COMSOL 1 May 30, 2008 05:35
OpenFOAM with Cygwin kitchener OpenFOAM Installation 6 April 25, 2006 00:09
Env variable not set gruber2 OpenFOAM Installation 5 December 30, 2005 05:27
Replace periodic by inlet-outlet pair lego CFX 3 November 5, 2002 21:09


All times are GMT -4. The time now is 00:26.