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

UDF for critical strain rate to extinction

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

LinkBack Thread Tools Search this Thread Display Modes
Old   July 10, 2006, 05:36
Default UDF for critical strain rate to extinction
Birute Bunkute
Posts: n/a
Hello everyone

I am using partially premixed combustion model with propane. My problem arises when I try to define critical strain rate to extinction g_cr=U^2/alpha, where U is laminar burning velocity and alpha is thermal diffusivity. Fluent compiles or interprets UDF without any problem (I tried both options). My "headache" starts when I hook UDF. Fluent gives following error:


FLUENT received fatal signal (ACCESS_VIOLATION) 1. Note exact events leading to error. 2. Save case/data under new name. 3. Exit program and restart to continue. 4. Report error to your distributor. Error Object: ()

Interrupting... Done.

This is a very simple UDF:

/************************************************** ********* strain1.c UDF for critical strain rate to extinction ************************************************** *********/

#include "udf.h"

#include "sg_mem.h"

DEFINE_PROPERTY(critical_strain_rate,c,t) { real S_ext; real alpha_c; real u_lam = C_LAM_FLAME_SPEED(c,t); real k_c = C_K_L(c,t); real rho_c = C_R(c,t); real cp_c = C_CP(c,t); alpha_c = k_c/(rho_c*cp_c); S_ext = (u_lam*u_lam)/alpha_c;

return S_ext; }

I will appreciate for any hints and tips, how I could solve this problem.

Thanks, Birute

  Reply With Quote

Old   March 25, 2010, 15:40
New Member
Join Date: Mar 2009
Posts: 5
Rep Power: 17
cryogenicT is on a distinguished road

This (too) late, this is not a fix. It's rather a conceptual matter.
You need the "unburnt" thermal diffusivity for the expression of the critical rate of strain, that is you need to use the unburnt mixture properties. I wrote a UDF for that but I use mean mixture fraction polynomial curve fits to compute the unburnt thermal diffusivity (you can get these from Fluent). However, for some reason, it's not giving me what I expect. Did you manage to figure out how to do this eventually?

cryogenicT is offline   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
strain rate in UDF Paulina FLUENT 11 November 20, 2014 03:06
strain rate magnitude ahmadbakri STAR-CCM+ 1 June 3, 2010 13:03
UDF for the critical rate of strain. cryogenicT FLUENT 0 March 25, 2010 15:52
Strain rate. MM? Main CFD Forum 1 February 15, 2006 08:55
strain rate at arbitrary position in a cell K. Kevala FLUENT 0 February 4, 2004 17:14

All times are GMT -4. The time now is 07:51.