CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Fluent UDF and Scheme Programming

DEFINE_DIFFUSIVITY udf in fluent

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

Reply
 
LinkBack Thread Tools Display Modes
Old   August 10, 2013, 11:57
Question DEFINE_DIFFUSIVITY udf in fluent
  #1
New Member
 
Mariusz
Join Date: Aug 2013
Posts: 2
Rep Power: 0
maniek940 is on a distinguished road
Hello,
I am new user of fluent and I need udf for traser diffusivity in water. The traser is flowing from small pipe to bigger, filled with water. In manual I found only example for mean age of air, so please help me. I use k-epsilon model.

The equation of traser diffusion is:
D=(Dm+Dt)*rho

where:
Dm and rho are constant,

Dt=0.1*(k^2/epsilon)
k and epsilon are values calculated by fluent in every cell,

The udf function I need is DEFINE_DIFFUSIVITY(name,c,t,i)
in manual there was an information that c,t,i are variables, but I don't know how they are working.

Can anyone help me how to create udf, that fluent can "understand" that k and epsilon are that values calculated?
maniek940 is offline   Reply With Quote

Old   August 11, 2013, 13:12
Default
  #2
Senior Member
 
A CFD free user's Avatar
 
A-A Azarafza
Join Date: Jan 2013
Posts: 187
Rep Power: 4
A CFD free user is on a distinguished road
Quote:
Originally Posted by maniek940 View Post
Hello,
I am new user of fluent and I need udf for traser diffusivity in water. The traser is flowing from small pipe to bigger, filled with water. In manual I found only example for mean age of air, so please help me. I use k-epsilon model.

The equation of traser diffusion is:
D=(Dm+Dt)*rho

where:
Dm and rho are constant,

Dt=0.1*(k^2/epsilon)
k and epsilon are values calculated by fluent in every cell,

The udf function I need is DEFINE_DIFFUSIVITY(name,c,t,i)
in manual there was an information that c,t,i are variables, but I don't know how they are working.

Can anyone help me how to create udf, that fluent can "understand" that k and epsilon are that values calculated?
Hey Dude
You can do it either by defining a generic user scalar function (UDS) or applying species transport equation. The most important thing is the diffusivity, of course which you can use DIFFUSIVITY macro. The macro has four arguments: "name" is the name you consider for the function, "c" stands for the cells (cells in the zone), "t" designates thread (actually it represents zone ) and finally "i" is an index which imply to the interest species (the species you want to define a diffusivity). It is defined according to the order you select the species. For instance, if you have three specie, "i" is 0,1 and 2 for the specie, respectively. Let me tell you that if you use UDS then you can find the "i" for the appropriate scalar in user define/ scalars/ UDS index.
I hope it helps somehow
__________________
Regard yours
A CFD free user is offline   Reply With Quote

Old   August 13, 2013, 17:13
Default
  #3
New Member
 
Mariusz
Join Date: Aug 2013
Posts: 2
Rep Power: 0
maniek940 is on a distinguished road
Hey Azarafza,
It helped, thanks so much
maniek940 is offline   Reply With Quote

Reply

Tags
define_diffusivity, diffusion, diffusivity, udf

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
fluent udf, saving data in udf mohsen zendehbad Fluent UDF and Scheme Programming 13 March 21, 2014 16:36
Transient pressure UDF for parallel fluent droberts Fluent UDF and Scheme Programming 5 October 11, 2010 04:13
Using Fluent with a UDF frm a remote m/c aarti FLUENT 2 September 11, 2008 19:53
UDF problem caused by various version of Fluent Yurong FLUENT 3 January 15, 2006 11:57
Can somebody send me a Fluent 6 UDF manual?? KKLAU FLUENT 4 April 14, 2004 16:37


All times are GMT -4. The time now is 04:55.