CFD Online Logo CFD Online URL
Home > Forums > Software User Forums > ANSYS > FLUENT

UDF for Drag

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

LinkBack Thread Tools Search this Thread Display Modes
Old   December 21, 2006, 11:12
Default UDF for Drag
Posts: n/a
Anyone have used or using UDF for defining Cd for speheres in a gas-particle flow...? In other words anyone has used DEFINE_DPM_DRAG, given by fluent...?

I have a question/doubt in that UDF.

Fluent wants the user to return a non-dimensional number as drag number, which is equivalent to 18*Cd*Re/24. But how does a drag force be dimensionless....If it is Cd it makes sense...but how a drag force is non-dimensionless...?

Please clarify!
  Reply With Quote

Old   January 2, 2007, 07:13
Default Re: UDF for Drag
Posts: n/a
I have written UDFs using DEFINE_DPM_DRAG. That macro must return a value for (18*Cd*Re/24) to Fluent. The drag force is then calculated as FD = (18*Cd*Re/24)*(my/(rho_p*d_p^2)), as stated in the Fluent manual. This might seem a bit strange but it does not cause you any problems, really? As both Cd and Re_p are dimensionless, the product (18*Cd*Re/24) is of course also dimensionless.

  Reply With Quote


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
Dynamic Mesh UDF Qureshi FLUENT 7 March 23, 2017 07:37
UDF parallel error: chip-exec: function not found????? shankara.2 Fluent UDF and Scheme Programming 1 January 16, 2012 22:14
How to add a UDF to a compiled UDF library kim FLUENT 3 October 26, 2011 21:38
UDF...UDF...UDF...UDF Luc SEMINEL FLUENT 0 November 25, 2002 04:03
UDF, UDF, UDF, UDF Luc SEMINEL Main CFD Forum 0 November 25, 2002 04:01

All times are GMT -4. The time now is 07:20.