[alinik]

I know that this is a general error but thought someone might be able to help as I am sure many have faced this problem.

I am having a UDF and I think that the C_UDSI_G (gradient of a user defined scalar) is causing this error. Apparently this error occurs whenever we would like to access a variable that is not available.

Does anybody have a solution to this?

Thanks,

Ali

[alinik]

I have excluded the gradient terms in UDF and have put some constants there instead. I am still receiving the same error.

Anyone?

[SJSW]

"this error occurs whenever we would like to access a variable that is not available"

Maybe you can go to find a method to get the value of the variable?

[`e`]

What is your UDF and have you found the line of code that is causing the error?

[alinik]

Hi 'e'

Sorry it has been a while and I was finishing something else.
I printed out messages at different lines in the code to see where the error is being generated and observed this line is causing the error:

thread_loop_c (t,domain)

I use this line in an adjust macro.
Any ideas?

Thanks,
Ali

[`e`]

What is your UDF code? Have you appropriately declared/initialised the 't' and 'domain' variables?

[SJSW]

Originally Posted by alinik

Hi 'e'

Sorry it has been a while and I was finishing something else.
I printed out messages at different lines in the code to see where the error is being generated and observed this line is causing the error:

thread_loop_c (t,domain)

I use this line in an adjust macro.
Any ideas?

Thanks,
Ali

Hi~
How do you print out messages at different lines in the code to see where the error is being generated?
Thank you!

[Bruno Machado]

Originally Posted by SJSW

Hi~
How do you print out messages at different lines in the code to see where the error is being generated?
Thank you!

put Message through your code and see where it stops. Then you can direct you debug.

Message("1");
.
.
.
Message("2");

[alinik]

Hi folks,

I am still having this problem.
Whenever I want to use C_UDSI_G I get segmentation error. I have traced the error and I am 100% sure that this is causing the error.

Any one has any similar experience?

Thanks,

Ali

[SJSW]

I found some information in
http://jullio.pe.kr/fluent6.1/help/html/udf/node107.htm

「
UDF used to calculate gradient for post-processing

User defined scaler (UDS) and user defined memory (UDM) are used.
For any UDS, Fluent will automatically calculate the gradient. So,
we need to pass the variable to UDS, and fluent will calculate the
gradient for you. UDM is used to save the results.

Steps to take to make it work:
1. Build UDF library
2. Read in the converged case and data
3. Hook the UDF (Define->User Defined->Function->Compiled)
4. Hook adjust function (Define->User Defined->Function Hooks->
Adjust Function)
5. Define UDM (Define->User Defined->Memory 1)
6. Define UDS (Define->User Defined->Scalars 1)
7. Define BC for UDS (the same as the function for which you
want gradient)
8. Change UR for UDS to 1e-6 (Solve->Controls->Solution)
9. Turn off all equations except UDS (Solve->Controls->Solution)
10 Do A FEW iterations
11 Execute store_gradient (Define->User Defined->Execute On Demand)

NOTES on item 7 8 and 9
step 7 is VERY IMPORTANT, otherwise the gradient close to the
boundary will not be correct.
step 8 is VERY IMPORTANT, otherwise the solution will change.
Fluent will try to solve an equation for UDS; we want to
force it to be unchanged.
step 9 will save you time as the solution is already converged.
step 10 Three is determined to be the minimum.
」

[bharathcfd]

Hi I am new to fluent
I received a
Error : fatal signal (segmentation fault)
Error object : #f for the following udf in defining nano fluid properties please help me in solving.
#include "udf.h"
#define FI 0.1
#define RHO_np 3600
#define SI_1 0.9830
#define SI_2 12.959
#define KTC_np 30
#define TI 5E4
#define BETA_1 8.4407
#define BETA_2 -1.07304
#define CP_w 4200
#define KA 1.383E-23
#define SIi_1 2.8217E-2
#define SIi_2 3.917E-3
#define SIi_3 -3.0669E-2
#define SIi_4 -3.91123E-3
#define T_0 298.15
#define D_np 59E-9
#define CP_np 785
DEFINE_PROPERTY(cell_conductivity,cell,thread)
{
real ktc,ktc_w,temp,f,beta;
temp = C_T(cell,thread);
f = ((SIi_1*FI+SIi_2)*temp/T_0)+(SIi_3*FI+SIi_4);
beta = BETA_1*(pow(100*FI,BETA_2));
ktc_w = (-8.354*0.000001*(pow(temp,2)))+((6.53*0.001*temp)-0.5981);
ktc = ((KTC_np+(2*ktc_w)-2*(ktc_w-KTC_np)*FI)/(KTC_np+(2*ktc_w)+(ktc_w-KTC_np)*FI))*ktc_w+(TI*beta*FI*CP_w*(pow(((KA*temp )/(RHO_np*D_np)),0.5))*f);
return ktc;
}

DEFINE_PROPERTY(cell_density,cell,thread)
{
real temp,rho_w,rho;
temp = C_T(cell,thread);
rho_w = (-3.570*(pow(10,-3))*(pow(temp,2))+1.88*temp+753.2);
rho = (FI*RHO_np)+((1-FI)*rho_w);
return rho;
}

DEFINE_PROPERTY(cell_viscosity,cell,thread)
{
real mu,mu_w,temp;
temp = C_T(cell,thread);
mu_w = (2.591*(pow(10,-5))*(pow(10,(238.3/(temp-143.2)))));
mu = (SI_1*exp(SI_2*FI)*mu_w);
return mu;
}

DEFINE_PROPERTY(cell_specificheat,cell,thread)
{
real temp,cp,cp_w,rho_w,rho,T;
temp = C_T(cell,thread);
rho_w = (-3.570*(pow(10,-3))*(pow(T,2))+(1.88*T+753.2));
rho = (FI*RHO_np)+((1-FI)*rho_w);
cp_w = 4.2174356-0.0056181625*temp+0.0012992528*pow(temp,1.5)-0.00011535353*pow(temp,2.0)+4.14964*pow(10.0,-6.0)*pow(temp,2.5);
cp = ((FI*RHO_np*CP_np)+((1-FI)*rho_w*CP_w))/rho;
return cp;
}


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[SJSW]

Maybe you can try the method from Bruno Machado at #8 in this thread.
Try to insert 「Message("1");」 between lines, and find out which line would result in the problem.

[furqanrk]

Hi everyone !

I hope you are fine. I am using UDF in VOF model in ANSYS FLUENT, although, my VOF model without UDF is running fine. The UDF is written by my friend used it successfully. He has graduated last year after getting the results from same UDF. The UDF was working well on his server. He was using Fluent 6.3 on Linux system. When I am using same case, date and UDF on my laptop the case is not running, although UDF compilation is very fine. I also check it on Linux system too. During or after initialization, Error occurred segmentation fault error. It is very strange that same case and UDF is not working on his office now. Main error occurred when I am hooking ADJUST and EXECUTE-AT-END UDFs. May be there is some problem of writing/calling style is different in Windows and Linux system with 32bit and 64bit. ( this is just my opinion).

I hope you can understand the situation and have a try to fix the problem. I would be highly thankful if you guide me that where is the problem. I can send UDF by email if needed..

Thanks in Advance,
Regards,
M. F. ALi

[SJSW]

1.The syntax could be different in different FLUENT version.
2.The order of declaration of the variables could be a major problem in different OS such as Windows and Linux.
It seems that the order could be more casual in Linux than in Windows.
3.The compiler is not installed completely.
4.The environment variables are not well set up.

[newton2009]

Hi My Good Friends, I am a master student and for my thesis.
I wrote a udf for importing nano fluid properties in a 2D simple geometry by Fluent.
my case is:
laminar
single phase
I wrote udf and compiled it without any error when I want to initialize the case in fluent gave error please help me to find the reason
my udf is:
/************************************************** ************/
/* */
/* User-Defined Functions for temperature-dependent viscosity */
/* density , conductivity and heat capacity of */
/* Ansys FLUENT 18.2 */

#include "udf.h"

real phi=0;
real kp=35;
real rhop=3890;
real cp=880;
real dp=10;
real alphap=0.00001022435;
DEFINE_PROPERTY(cell_conductivity,cell,thread)
{
real knf;
real kb;
real mub;
real rhob;
real alphab;
real T=C_T(cell,thread)-273.15;
kb=0.56112+0.00193*T-0.0000026015*pow(T,2)-0.0000000608803*pow(T,3);
mub=0.00169-0.000042526*T+0.00000049255*pow(T,2)-0.00000000209935*pow(T,3);
rhob=(1000*(119000+(T*1365)-4*pow(T,2)-pow((T-4),2)))/(119000+(T*1365)-4*pow(T,2));
alphab=kb/(rhob*mub);
knf=kb*0.8938*pow(1+(phi/100),1.37)*pow(1+(T/70),0.2777)*pow(1+(dp/150),-0.0336)*pow((alphap/alphab),0.01737);
return knf;
}
DEFINE_PROPERTY(cell_density,cell,thread)
{
real T=C_T(cell,thread)-273.15;
real rhob;
real rhonf;
rhob=1000*(119000+(T*1365)-4*pow(T,2)-pow((T-4),2))/(119000+(T*1365)-4*pow(T,2));
rhonf=(1-phi)*rhob+phi*(rhop);
return rhonf;
}
DEFINE_PROPERTY(cell_viscosity, cell, thread)
{
real munf;
real T , mub;
T=C_T(cell,thread)-273.15;
mub=0.00169-0.000042526*T+0.00000049255*pow(T,2)-0.00000000209935*pow(T,3);
munf=mub*pow(1+(phi/100),11.3)*pow(1+(T/70),-0.038)*pow(1+(dp/170),-0.061);
return munf;
}
DEFINE_PROPERTY(cell_specificheat, cell, thread)
{
real rhob;
real rhonf;
real cnf;
real T, cb;
T = C_T(cell, thread) - 273.15;
rhob = 1000 * (119000 + (T * 1365) - 4 * pow(T, 2) - pow((T - 4), 2)) / (119000 + (T * 1365) - 4 * pow(T, 2));
rhonf = (1 - phi)*rhob + phi*(rhop);
cb = 4217.629-3.20888*T + 0.09503*pow(T, 2) - 0.00132*pow(T, 3)+0.000009415*pow(T, 4)-0.000000025479*pow(T, 5);
cnf = ((1-phi)*(rhob*cb)+phi*(rhop*cp))/((1-phi)*rhob+phi*rhop);
return cnf;
}

[SJSW]

What is the error message?
You can post here.
I think that you can check if any value used in the UDF was missed in the setting pages.

Originally Posted by newton2009

Hi My Good Friends, I am a master student and for my thesis.
I wrote a udf for importing nano fluid properties in a 2D simple geometry by Fluent.
my case is:
laminar
single phase
I wrote udf and compiled it without any error when I want to initialize the case in fluent gave error please help me to find the reason
my udf is:
/************************************************** ************/
/* */
/* User-Defined Functions for temperature-dependent viscosity */
/* density , conductivity and heat capacity of */
/* Ansys FLUENT 18.2 */

#include "udf.h"

real phi=0;
real kp=35;
real rhop=3890;
real cp=880;
real dp=10;
real alphap=0.00001022435;
DEFINE_PROPERTY(cell_conductivity,cell,thread)
{
real knf;
real kb;
real mub;
real rhob;
real alphab;
real T=C_T(cell,thread)-273.15;
kb=0.56112+0.00193*T-0.0000026015*pow(T,2)-0.0000000608803*pow(T,3);
mub=0.00169-0.000042526*T+0.00000049255*pow(T,2)-0.00000000209935*pow(T,3);
rhob=(1000*(119000+(T*1365)-4*pow(T,2)-pow((T-4),2)))/(119000+(T*1365)-4*pow(T,2));
alphab=kb/(rhob*mub);
knf=kb*0.8938*pow(1+(phi/100),1.37)*pow(1+(T/70),0.2777)*pow(1+(dp/150),-0.0336)*pow((alphap/alphab),0.01737);
return knf;
}
DEFINE_PROPERTY(cell_density,cell,thread)
{
real T=C_T(cell,thread)-273.15;
real rhob;
real rhonf;
rhob=1000*(119000+(T*1365)-4*pow(T,2)-pow((T-4),2))/(119000+(T*1365)-4*pow(T,2));
rhonf=(1-phi)*rhob+phi*(rhop);
return rhonf;
}
DEFINE_PROPERTY(cell_viscosity, cell, thread)
{
real munf;
real T , mub;
T=C_T(cell,thread)-273.15;
mub=0.00169-0.000042526*T+0.00000049255*pow(T,2)-0.00000000209935*pow(T,3);
munf=mub*pow(1+(phi/100),11.3)*pow(1+(T/70),-0.038)*pow(1+(dp/170),-0.061);
return munf;
}
DEFINE_PROPERTY(cell_specificheat, cell, thread)
{
real rhob;
real rhonf;
real cnf;
real T, cb;
T = C_T(cell, thread) - 273.15;
rhob = 1000 * (119000 + (T * 1365) - 4 * pow(T, 2) - pow((T - 4), 2)) / (119000 + (T * 1365) - 4 * pow(T, 2));
rhonf = (1 - phi)*rhob + phi*(rhop);
cb = 4217.629-3.20888*T + 0.09503*pow(T, 2) - 0.00132*pow(T, 3)+0.000009415*pow(T, 4)-0.000000025479*pow(T, 5);
cnf = ((1-phi)*(rhob*cb)+phi*(rhop*cp))/((1-phi)*rhob+phi*rhop);
return cnf;
}