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

Help on accessing volume fraction in mixture model

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   April 20, 2009, 14:14
Default Help on accessing volume fraction in mixture model
  #1
New Member
 
Aditya Chunekar
Join Date: Mar 2009
Posts: 18
Rep Power: 17
achuneka is on a distinguished road
I am writing a UDF that involves volume fraction for Unsteady RANS simulation with cavitation model turned on.

I define a user defined memory variable and use the following snippet of code to access it.

DEFINE_EXECUTE_AT_END(udf_name)
{
........ /* All the definitions */

d=Get_Domain(3); /* Vapor Phase domain

thread_loop_c(t,d)
{
begin_c_loop(c,t)
{
C_UDMI(c,t,1)=C_VOF(c,t);
}
}
end_c_loop(c,t)
}
}
(This is just to show how I access C_VOF.. I perform some other operations on it)

I get the value of C_UDMI(c,t,1) as 0 everywhere when the volume fraction of phase 2 varies from 0 to 0.4.

Can someone please help me on the same. Thanks
achuneka is offline   Reply With Quote

Old   April 20, 2009, 15:03
Default
  #2
New Member
 
Aditya Chunekar
Join Date: Mar 2009
Posts: 18
Rep Power: 17
achuneka is on a distinguished road
I think the problem is with C_UDMI, since I can modify the values of volume fraction using C_VOF variable.

I guess the problem is def of C_UDMI for the mixture domain. Is there any way to define a C_UDMI for a phase ?
achuneka is offline   Reply With Quote

Old   April 20, 2009, 15:57
Default
  #3
New Member
 
Aditya Chunekar
Join Date: Mar 2009
Posts: 18
Rep Power: 17
achuneka is on a distinguished road
I found something strange.
The initial contours of void fraction show the values in the range of 0 to 0.4

thread_loop_c(t,d)
{
begin_c_loop(c,t)
{
if(index==1)
{
C_UDMI(c,t,1)=C_VOF(c,t); /* >>>>> Over here C_VOF(c,t) is approx 0
C_VOF(c,t) = 1 ; /** Some arbit modification
}
}
end_c_loop(c,t)
}

Now if I check out the contours of volume fraction for phase 2 it shows 1 everywhere... !

So somehow C_VOF does not get the initial data on void fraction....
Am i doing something obviuosly wrong ? pls let me know ..
achuneka is offline   Reply With Quote

Old   April 21, 2009, 11:30
Default
  #4
New Member
 
Join Date: Apr 2009
Posts: 4
Rep Power: 17
cfdpinku is on a distinguished road
hello aditya,
i hope you are aware that there are some special multiphase macros avaialble.
i am sure your required domain is not passing with get_domain.
can you please try once with domain_sub_domain.... you can find more details on this in UDF manual.
i hope fluent support can help you on this.
cfdpinku is offline   Reply With Quote

Old   April 21, 2009, 13:02
Default
  #5
New Member
 
Aditya Chunekar
Join Date: Mar 2009
Posts: 18
Rep Power: 17
achuneka is on a distinguished road
Thanks,
But the fact that I am able to modify the value of volume fraction of phase 2 through the same loop means that I am passing the phase domain to the loop. Somehow the current values are not being accessed.

I have contacted Fluent support.. Hope they help me on it
achuneka is offline   Reply With Quote

Old   April 22, 2009, 11:42
Default
  #6
New Member
 
Join Date: Apr 2009
Posts: 4
Rep Power: 17
cfdpinku is on a distinguished road
i hope domain_id =3 what you have used is picked from define->phases, for vapour phase. since domain id are not necessarily sequential. if this is correct, would you mind sharing sample case with me. i can help you on that. i have tested at my end it works fine.
cfdpinku is offline   Reply With Quote

Old   April 23, 2009, 13:30
Default
  #7
New Member
 
Aditya Chunekar
Join Date: Mar 2009
Posts: 18
Rep Power: 17
achuneka is on a distinguished road
cfdpinku,

Cannot upload the file over here. Exeeds the file limit
Can you please pm me your email ed ? The total size is around 4 mb

Aditya
achuneka is offline   Reply With Quote

Old   September 4, 2009, 06:21
Default
  #8
New Member
 
asif nazir
Join Date: Aug 2009
Posts: 3
Rep Power: 17
asifnazir is on a distinguished road
hi u should go into subdomain thread then it work
asifnazir is offline   Reply With Quote

Old   September 4, 2009, 06:22
Smile
  #9
New Member
 
asif nazir
Join Date: Aug 2009
Posts: 3
Rep Power: 17
asifnazir is on a distinguished road
THREAD_SUB_THREAD look this macro from the manual
asifnazir is offline   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
udf: volume fraction gradient in eulerian model jwwang FLUENT 22 April 15, 2015 06:27
Weighted average volume fraction Yasser FLUENT 5 April 11, 2015 08:25
Superlinear speedup in OpenFOAM 13 msrinath80 OpenFOAM Running, Solving & CFD 18 March 3, 2015 05:36
Volume Fraction in VOF model Saima Main CFD Forum 2 April 12, 2009 19:22
UDF for the mixture model khar nab FLUENT 0 July 31, 2008 06:29


All times are GMT -4. The time now is 23:20.