fatal signal segmentation fault

flo90000 · June 7, 2016, 12:02

Hello,

when I want to run a simulation in transient with some UDFs and 6DOF in Fluent 17. I have this error which appears

Error: received a fatal signal (Segmentation fault).
Error Object: #f

After some research on this error, I have found that this error appears when we are trying to access some internal variables of FLUENT solver in the UDF. I don't know why or where there are some errors because it used in a tutorial and it works well. There are the modified UDFs which I use.

Code:

#include "udf.h"
#define X_MAX 0.0575
#define X_MIN 0.05732
#define Y_MAX 0.0554
#define Y_MIN 0.05524 
#define C2 50000.0
DEFINE_SOURCE(xmom_source_2,c,t,dS,eqn)
 {
    real pos[ND_ND];
    real con, source, x, y;
    int i;
	C_CENTROID(pos,c,t);
	x = pos[0];
	y = pos[1];
	i = 0;
	if (x > X_MIN) i++;
	if (x < X_MAX) i++;
	if (y > Y_MIN) i++;
	if (y < Y_MAX) i++;
	if (i == 4)
		{con = C2*0.5*C_R(c,t);
		source = -con*fabs(C_U(c, t))*C_U(c,t);
		dS[eqn] = -2.*con*fabs(C_U(c,t));}
	else
		source=0;
	C_UDMI(c,t,0)=source;
	return source;
 } 
DEFINE_SOURCE(ymom_source_2,c,t,dS,eqn)
 {
    real pos[ND_ND];
    real con, source, x, y;
    int i;
	C_CENTROID(pos,c,t);
	x = pos[0];
	y = pos[1];
	i = 0;
	if (x > X_MIN) i++;
	if (x < X_MAX) i++;
	if (y > Y_MIN) i++;
	if (y < Y_MAX) i++;
	if (i == 4)
		{con = C2*0.5*C_R(c,t);
		source = -con*fabs(C_V(c, t))*C_V(c,t);
		dS[eqn] = -2.*con*fabs(C_V(c,t));}
	else
		source=0;
	C_UDMI(c,t,1)=source;
	return source;
 }

Code:

#include "udf.h"

DEFINE_SDOF_PROPERTIES(Clapet_1, prop, dt, time, dtime)
{
	
	prop[SDOF_MASS] = 1.067e-7;
	prop[SDOF_IZZ] = 5,33e-11;
	prop[SDOF_ZERO_TRANS_X] = TRUE;
	prop[SDOF_ZERO_TRANS_Y] = TRUE;
	prop[SDOF_ZERO_TRANS_Z] = TRUE;
	prop[SDOF_ZERO_ROT_X] = TRUE;
	prop[SDOF_ZERO_ROT_Y] = TRUE;
	prop[SDOF_ZERO_ROT_Z] = FALSE;
		
}

DEFINE_SDOF_PROPERTIES(Clapet_2, prop, dt, time, dtime)
{
	
	prop[SDOF_MASS] = 1.067e-7;
	prop[SDOF_IZZ] = 5,33e-11;
	prop[SDOF_ZERO_TRANS_X] = TRUE;
	prop[SDOF_ZERO_TRANS_Y] = TRUE;
	prop[SDOF_ZERO_TRANS_Z] = TRUE;
	prop[SDOF_ZERO_ROT_X] = TRUE;
	prop[SDOF_ZERO_ROT_Y] = TRUE;
	prop[SDOF_ZERO_ROT_Z] = FALSE;
		
}

Thank you in advance for your help.

Bruno Machado · June 7, 2016, 12:17

Quote:

Originally Posted by flo90000

Hello,

when I want to run a simulation in transient with some UDFs and 6DOF in Fluent 17. I have this error which appears

Error: received a fatal signal (Segmentation fault).
Error Object: #f

After some research on this error, I have found that this error appears when we are trying to access some internal variables of FLUENT solver in the UDF. I don't know why or where there are some errors because it used in a tutorial and it works well. There are the modified UDFs which I use.

Code:

#include "udf.h"
#define X_MAX 0.0575
#define X_MIN 0.05732
#define Y_MAX 0.0554
#define Y_MIN 0.05524 
#define C2 50000.0
DEFINE_SOURCE(xmom_source_2,c,t,dS,eqn)
 {
    real pos[ND_ND];
    real con, source, x, y;
    int i;
	C_CENTROID(pos,c,t);
	x = pos[0];
	y = pos[1];
	i = 0;
	if (x > X_MIN) i++;
	if (x < X_MAX) i++;
	if (y > Y_MIN) i++;
	if (y < Y_MAX) i++;
	if (i == 4)
		{con = C2*0.5*C_R(c,t);
		source = -con*fabs(C_U(c, t))*C_U(c,t);
		dS[eqn] = -2.*con*fabs(C_U(c,t));}
	else
		source=0;
	C_UDMI(c,t,0)=source;
	return source;
 } 
DEFINE_SOURCE(ymom_source_2,c,t,dS,eqn)
 {
    real pos[ND_ND];
    real con, source, x, y;
    int i;
	C_CENTROID(pos,c,t);
	x = pos[0];
	y = pos[1];
	i = 0;
	if (x > X_MIN) i++;
	if (x < X_MAX) i++;
	if (y > Y_MIN) i++;
	if (y < Y_MAX) i++;
	if (i == 4)
		{con = C2*0.5*C_R(c,t);
		source = -con*fabs(C_V(c, t))*C_V(c,t);
		dS[eqn] = -2.*con*fabs(C_V(c,t));}
	else
		source=0;
	C_UDMI(c,t,1)=source;
	return source;
 }

Code:

#include "udf.h"

DEFINE_SDOF_PROPERTIES(Clapet_1, prop, dt, time, dtime)
{
	
	prop[SDOF_MASS] = 1.067e-7;
	prop[SDOF_IZZ] = 5,33e-11;
	prop[SDOF_ZERO_TRANS_X] = TRUE;
	prop[SDOF_ZERO_TRANS_Y] = TRUE;
	prop[SDOF_ZERO_TRANS_Z] = TRUE;
	prop[SDOF_ZERO_ROT_X] = TRUE;
	prop[SDOF_ZERO_ROT_Y] = TRUE;
	prop[SDOF_ZERO_ROT_Z] = FALSE;
		
}

DEFINE_SDOF_PROPERTIES(Clapet_2, prop, dt, time, dtime)
{
	
	prop[SDOF_MASS] = 1.067e-7;
	prop[SDOF_IZZ] = 5,33e-11;
	prop[SDOF_ZERO_TRANS_X] = TRUE;
	prop[SDOF_ZERO_TRANS_Y] = TRUE;
	prop[SDOF_ZERO_TRANS_Z] = TRUE;
	prop[SDOF_ZERO_ROT_X] = TRUE;
	prop[SDOF_ZERO_ROT_Y] = TRUE;
	prop[SDOF_ZERO_ROT_Z] = FALSE;
		
}

Thank you in advance for your help.

check if it works with/without the momentum source terms. so them you can eliminate parts of your code that are not causing the problem.

other suggestion is to add couple of printing messages in your code so then you can see up to which part it works and locate the error easily. try to use
add this to different parts of your code.

Message("1");
Message("2");
Message("3");
Message("...");

`e` · June 7, 2016, 18:09

Use decimal places instead of commas in numbers:

Code:

prop[SDOF_IZZ] = 5,33e-11;

flo90000 · June 8, 2016, 09:30

Quote:

Originally Posted by Bruno Machado

check if it works with/without the momentum source terms. so them you can eliminate parts of your code that are not causing the problem.

other suggestion is to add couple of printing messages in your code so then you can see up to which part it works and locate the error easily. try to use
add this to different parts of your code.

Message("1");
Message("2");
Message("3");
Message("...");

I changed the decimal places instead of commas and added some messages in the UDFs as you said. When I run without the momentum source terms, it doesn't work too. But it is writen "6DOF angular has not converged" after the message for the update of properties.

pakk · June 8, 2016, 10:44

Did you add a user defined memory?

flo90000 · June 8, 2016, 11:38

Quote:

Originally Posted by pakk

Did you add a user defined memory?

No, I didn't add a user defined memory. How do we know the number of UDM and UDNM locations. Does a macro exist to modify them automatically?

pakk · June 8, 2016, 13:51

Quote:

Originally Posted by flo90000

No, I didn't add a user defined memory. How do we know the number of UDM and UDNM locations. Does a macro exist to modify them automatically?

I saw in your code that you use one user defined memory:

Code:

C_UDMI(c,t,0)=source;

This should ideally be mentioned somewhere where you found this code. But try what happens after you add one user defined memory location.

flo90000 · June 9, 2016, 04:25

Quote:

Originally Posted by pakk

I saw in your code that you use one user defined memory:

Code:

C_UDMI(c,t,0)=source;

This should ideally be mentioned somewhere where you found this code. But try what happens after you add one user defined memory location.

I add the user defined location necessary but i have the same error of convergence.

pakk · June 9, 2016, 04:28

The change I suggested does not affect convergence issues, only segmentation faults. Your original question was about segmentation faults.

Bruno Machado · June 9, 2016, 04:31

Quote:

Originally Posted by flo90000

I add the user defined location necessary but i have the same error of convergence.

convergence or segmentation fault?

flo90000 · June 9, 2016, 04:45

Quote:

Originally Posted by pakk

I saw in your code that you use one user defined memory:

Code:

C_UDMI(c,t,0)=source;

This should ideally be mentioned somewhere where you found this code. But try what happens after you add one user defined memory location.

Quote:

Originally Posted by pakk

The change I suggested does not affect convergence issues, only segmentation faults. Your original question was about segmentation faults.

Quote:

Originally Posted by Bruno Machado

convergence or segmentation fault?

Sorry, I thought these two problems were linked.

Bruno Machado · June 9, 2016, 05:01

Quote:

Originally Posted by flo90000

Sorry, I thought these two problems were linked.

segmentation fault is related to he request of some information that is not available.

convergence is due to something wrong in the code that returns an unrealistic value. try to plot the values after initializing and see if they are what you expect.

hooman.esl · October 20, 2017, 08:48

Quote:

Originally Posted by Bruno Machado

segmentation fault is related to he request of some information that is not available.

convergence is due to something wrong in the code that returns an unrealistic value. try to plot the values after initializing and see if they are what you expect.

Hi Bruno,
I have written this code for momentum source term for a two-phase VOF model but I faced this error:
Error: received a fatal signal (Segmentation fault).
what wrong is with it?
do you have any idea which parameter is undefined?
thank you.

Quote:

#include "udf.h"
#define porosity 0.183 /*soil property porosity*/
#define sat_0_w 0.3 /*soil property residual water saturation*/
#define sat_0_g 0.1 // *************************shahab gerami page 134(table)**************************************** ******
#define k_abs 0.9671e-13 /* k: (intrinsic) permeability [L2] K: hydraulic conductivity [l/T ]=k rho gravity/nu */
DEFINE_SOURCE(source,c,t,dS,eqn)
{
Thread *mix_th, *water_th;
real k_avrg, rel_k_m, source, sat_w, relsat_w, rel_k_w;
mix_th = THREAD_SUPER_THREAD(t);
water_th = THREAD_SUB_THREAD(mix_th, 0);
sat_w = C_VOF(c,water_th);
relsat_w = (sat_w-sat_0_w)/(1-sat_0_g-sat_0_w);
rel_k_w = pow(relsat_w,4);
rel_k_m = (1-pow(relsat_w,2))*pow((1-relsat_w),(2));
k_avrg = rel_k_w*sat_w+rel_k_m*(1-sat_w);
source = -1*C_U(c,t)*C_MU_L(c,t)/(k_abs*k_avrg);
dS[eqn] = -1*C_MU_L(c,t)/(k_abs*k_avrg);
return source;
}

pakk · October 23, 2017, 04:40

C_U(c,t) or C_MU_L(c,t) (velocity or viscosity)

You try to define a source that needs information on velocity and viscosity. But apparently Fluent calculates this source before it calculates velocity and/or viscosity.

Solution: initialize your simulation without this UDF, and load the UDF afterwards.

hooman.esl · October 23, 2017, 09:39

Quote:

Originally Posted by pakk

C_U(c,t) or C_MU_L(c,t) (velocity or viscosity)

You try to define a source that needs information on velocity and viscosity. But apparently Fluent calculates this source before it calculates velocity and/or viscosity.

Solution: initialize your simulation without this UDF, and load the UDF afterwards.

Hi Pakk,
thank you for the reply.
i did it as you said and also i run the simulation for a second without the UDF that fluent calculate that parameters but, the error appeared again.

pakk · October 24, 2017, 04:40

Then find out what it by making a minimal example.

In the example below, I replaced C_U and C_MU_L by constants. Does it work now? Then the problem is in one of these two. Does it still not work? Then your problem is somewhere else.

Code:

#include "udf.h"
#define porosity 0.183 /*soil property porosity*/
#define sat_0_w 0.3 /*soil property residual water saturation*/
#define sat_0_g 0.1 // *************************shahab gerami page 134(table)**************************************** ******
#define k_abs 0.9671e-13 /* k: (intrinsic) permeability [L2] K: hydraulic conductivity [l/T ]=k rho gravity/nu */
DEFINE_SOURCE(source,c,t,dS,eqn)
{
Thread *mix_th, *water_th;
real k_avrg, rel_k_m, source, sat_w, relsat_w, rel_k_w;
mix_th = THREAD_SUPER_THREAD(t);
water_th = THREAD_SUB_THREAD(mix_th, 0);
sat_w = C_VOF(c,water_th);
relsat_w = (sat_w-sat_0_w)/(1-sat_0_g-sat_0_w);
rel_k_w = pow(relsat_w,4);
rel_k_m = (1-pow(relsat_w,2))*pow((1-relsat_w),(2));
k_avrg = rel_k_w*sat_w+rel_k_m*(1-sat_w);
source = -1e-6/(k_abs*k_avrg);
dS[eqn] = -1e-6*/(k_abs*k_avrg);
return source;
}

Find the simplest code that fails, and then you know where the problem is.

hooman.esl · October 26, 2017, 18:28

Quote:

Originally Posted by pakk

Then find out what it by making a minimal example.

In the example below, I replaced C_U and C_MU_L by constants. Does it work now? Then the problem is in one of these two. Does it still not work? Then your problem is somewhere else.

Code:

#include "udf.h"
#define porosity 0.183 /*soil property porosity*/
#define sat_0_w 0.3 /*soil property residual water saturation*/
#define sat_0_g 0.1 // *************************shahab gerami page 134(table)**************************************** ******
#define k_abs 0.9671e-13 /* k: (intrinsic) permeability [L2] K: hydraulic conductivity [l/T ]=k rho gravity/nu */
DEFINE_SOURCE(source,c,t,dS,eqn)
{
Thread *mix_th, *water_th;
real k_avrg, rel_k_m, source, sat_w, relsat_w, rel_k_w;
mix_th = THREAD_SUPER_THREAD(t);
water_th = THREAD_SUB_THREAD(mix_th, 0);
sat_w = C_VOF(c,water_th);
relsat_w = (sat_w-sat_0_w)/(1-sat_0_g-sat_0_w);
rel_k_w = pow(relsat_w,4);
rel_k_m = (1-pow(relsat_w,2))*pow((1-relsat_w),(2));
k_avrg = rel_k_w*sat_w+rel_k_m*(1-sat_w);
source = -1e-6/(k_abs*k_avrg);
dS[eqn] = -1e-6*/(k_abs*k_avrg);
return source;
}

Find the simplest code that fails, and then you know where the problem is.

I did that and found out that the problem is the part that i want to access the volume fraction of the primary phase( C_VOF(c,water_th)).
i dont know what to do with that.

June 7, 2016, 18:09		#3
`e` Senior Member Join Date: Mar 2015 Posts: 892 Rep Power: 18	Use decimal places instead of commas in numbers: Code: prop[SDOF_IZZ] = 5,33e-11;

October 23, 2017, 04:40		#14
pakk Senior Member Join Date: Nov 2013 Posts: 1,965 Rep Power: 26	C_U(c,t) or C_MU_L(c,t) (velocity or viscosity) You try to define a source that needs information on velocity and viscosity. But apparently Fluent calculates this source before it calculates velocity and/or viscosity. Solution: initialize your simulation without this UDF, and load the UDF afterwards. hooman.esl likes this.

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June 8, 2016, 10:44		#5
pakk Senior Member Join Date: Nov 2013 Posts: 1,965 Rep Power: 26	Did you add a user defined memory?

June 9, 2016, 04:28		#9
pakk Senior Member Join Date: Nov 2013 Posts: 1,965 Rep Power: 26	The change I suggested does not affect convergence issues, only segmentation faults. Your original question was about segmentation faults.