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

"""Source Term in UDS"""

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   April 10, 2003, 06:59
Default """Source Term in UDS"""
  #1
Sebeci
Guest
 
Posts: n/a
Hi every body I want to add a source term in UDS. Suppose the scalar is "fi" and the source is S=A+B*(fi)+C*(d(fi)/dx). How can I produce d(fi)/dx ?

Thanks for your help
  Reply With Quote

Old   April 10, 2003, 12:27
Default Re: """Source Term in UDS"""
  #2
Murali
Guest
 
Posts: n/a
<font face = "courier new">You do not "produce" the derivative. You just calculate the derivative and enter the expression. Refer to the example of adding a momentum source in the UDF manual under DEFINE_SOURCE. It clearly explains.</font>
  Reply With Quote

Old   April 12, 2003, 01:12
Default Re: """Source Term in UDS"""
  #3
Sebeci
Guest
 
Posts: n/a
Thank for your response, but my PDE is

[d^2(fi)/d(x^2)]+[d^2(fi)/d(y^2)]=A*[d(fi)/dt]+B*(fi) +C*(d(fi)/dx

so, I want to add A+B*(fi)+C*(d(fi)/dx as a source term.

How can I do it? Please explain more.

  Reply With Quote

Old   April 14, 2003, 14:54
Default Re: """Source Term in UDS"""
  #4
Murali
Guest
 
Posts: n/a
<font face = "courier new">I presume you are not too familiar with the macro stuff in F6. I strongly suggest you go through Chapter 5 of the UDF manual.

That said, your problem can be tackled by accessing the derivatives of the particular variable from F6. Refer to page 5-5 of UDF manual to set up F6 for accessing the gradient information. I presume that "fi" in your equation is a UDS. Hence the derivative of the UDS is accessed by C_UDSI_G(c,t,1)

Now when you specify a source term for a variable phi you are NOT required to find out the derivative of that variable with respect to spatial coordinate, BUT the partial derivative of the "sourece term" eith respect to the variable.

Hence if fi^2 is the source term then B = 2*fi. find your B similarly and use the macros to get your expression.

Regards

Murali</font>
  Reply With Quote

Old   April 14, 2003, 19:12
Default Re: """Source Term in UDS"""
  #5
Murali
Guest
 
Posts: n/a
A small correction:

if fi^2 is the source term then B = 2*fi.

Sorry. It should read:

if fi^2 is then derivative of source term = 2*fi. Hence A= 0 and B = phi and dS[1] = 2*fi

Regards

Murali
  Reply With Quote

Old   April 15, 2003, 04:55
Default Re: """Source Term in UDS"""
  #6
Sebeci
Guest
 
Posts: n/a
Thanks for your help murali As another question, In general form of UDS (chapter 9.2) I assumed ro(Density) as porosity(coefficient of d(fi)/dt) ,but in my problem the porosity varies in the cells.I have a database file of prosity and want to assign it to the cells. How it's possible?

Thank you in advance
  Reply With Quote

Old   April 16, 2003, 13:46
Default Re: """Source Term in UDS"""
  #7
Murali
Guest
 
Posts: n/a
<font face = "courier new">Sebeci:

Nice qn. As far as I know porosity "cannot" be a user modifiable function in F6. I suggest you discuss this with FLUENT people.

Murali </font>
  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
Problem of SOURCE term gradient in UDS wind Fluent UDF and Scheme Programming 6 December 1, 2022 15:21
momentum source term zwdi FLUENT 14 June 27, 2017 16:40
Large source term in species equation MACFD FLUENT 4 January 4, 2011 15:16
pressure gradient term in low speed flow Atit Koonsrisuk Main CFD Forum 2 January 10, 2002 11:52
bouyancy term in epsilon equation Michael Main CFD Forum 1 June 25, 1999 11:20


All times are GMT -4. The time now is 03:15.