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

Udf

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

Reply
 
LinkBack Thread Tools Display Modes
Old   March 3, 2010, 05:11
Default Udf
  #1
New Member
 
elsa
Join Date: Mar 2010
Posts: 7
Rep Power: 7
elsa is on a distinguished road
how can I define a function (UDF) in cfx? I have a specific thermal function (Pennes equation) for a hemisphere.
elsa is offline   Reply With Quote

Old   March 3, 2010, 06:51
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,662
Rep Power: 84
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
I have no idea what Penne equation is. This link tells me it is a heat transfer model used in physiology - http://jap.physiology.org/cgi/content/full/85/1/35 - I assume this is what you are talking about.

Looks like you will be able to implement this using source terms on the temperature/heat equation. I don't think you will need fortran. CEL expressions should work fine and they are MUCH easier.
ghorrocks is offline   Reply With Quote

Old   March 3, 2010, 14:22
Default Cel
  #3
New Member
 
elsa
Join Date: Mar 2010
Posts: 7
Rep Power: 7
elsa is on a distinguished road
thank you for your response.
yeah pennes is a bioheat equation.
could you please tell me more about CEL or give me a clue that where I can read about it.
thanks
elsa is offline   Reply With Quote

Old   March 3, 2010, 17:58
Default
  #4
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,662
Rep Power: 84
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
CFX documentation, reference manual - CEL Expression language.
ghorrocks is offline   Reply With Quote

Old   March 3, 2010, 23:07
Default heat flux
  #5
New Member
 
elsa
Join Date: Mar 2010
Posts: 7
Rep Power: 7
elsa is on a distinguished road
I have simulated a duct with constant walls temperature and air flow inside; how can I get the heat flux from one section of the duct to the other section? or is it possible to get the Nusselt number at one point in fully developed area?
elsa is offline   Reply With Quote

Old   March 4, 2010, 06:41
Default
  #6
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,662
Rep Power: 84
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
Nusselt number - Yes, define a new variable with an expression with the equation for Nusselt number in CFD-Post. Then you can view it, make contours of it and anything else you can do with variables.

Do you mean the heat flux from the air to the wall (look at the wall heat flux variable) or do you mean the heat flux from the convection of the air (make a surface which intersects the flow and define a new variable of density*Cp*normal velocity or something like that.)
ghorrocks is offline   Reply With Quote

Old   March 4, 2010, 14:18
Default
  #7
New Member
 
elsa
Join Date: Mar 2010
Posts: 7
Rep Power: 7
elsa is on a distinguished road
Thank you
actually, I'm looking for hat flux to find the convection coefficient or Nusselt number. if I can define the Nusselt number, there will be no necessity to calculate the heat flux.
the problem is I don't know how I can define the Nusselt number.
elsa is offline   Reply With Quote

Old   March 4, 2010, 16:45
Default
  #8
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,662
Rep Power: 84
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
As I said, in CFD-Post you need to define a new variable which is an equation to define Nusselt number. Then you can view it in CFD-Post. Have a look at the CFX tutorials, some of them will define variables in CFD-Post for post-processing.
ghorrocks is offline   Reply With Quote

Old   March 11, 2010, 00:05
Default
  #9
New Member
 
elsa
Join Date: Mar 2010
Posts: 7
Rep Power: 7
elsa is on a distinguished road
I already have written the Pennes equation by Fortran, how can I apply it in CFX?
elsa is offline   Reply With Quote

Old   March 12, 2010, 00:53
Default
  #10
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,662
Rep Power: 84
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
As I said, define a variable in CFD-Post and you can get it from there. If you are doing it in the solver then have a look in the CEL reference guide for the list of available variables - you will find wall heat transfer to be useful for you.
ghorrocks is offline   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
UDF parallel error: chip-exec: function not found????? shankara.2 Fluent UDF and Scheme Programming 1 January 16, 2012 23:14
How to add a UDF to a compiled UDF library kim FLUENT 3 October 26, 2011 21:38
Dynamic Mesh UDF Qureshi FLUENT 1 December 2, 2009 01:27
UDF...UDF...UDF...UDF Luc SEMINEL FLUENT 0 November 25, 2002 05:03
UDF, UDF, UDF, UDF Luc SEMINEL Main CFD Forum 0 November 25, 2002 05:01


All times are GMT -4. The time now is 14:18.