[Joe101]

Hi,

I have written a UDF to rotate an ellipse in 2D with a constant angular velocity. It has been compiled and loaded without any errors. However, when i come to preview the mesh motion i get the following error message:

"Updating mesh at time level N...
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: ()"

I cant work out the problem but i have a feeling it might be my udf as i am new to c programming. Here is a copy of the udf:

#include "udf.h"
DEFINE_CG_MOTION(ellipse, dt, vel, omega, time, dtime)
{
face_t f;
Thread *tf = DT_THREAD(dt); /* [5] */
Node *node;
real xn, yn, r, theta, y0, x0;
int n;
begin_f_loop(f,tf) /* Loops over all faces in the thread passed in the DEFINE macro argument [10] */
{
f_node_loop(f,tf,node) /* Loops over all nodes in the face */
{
xn = NODE_X(node); // calculate x-coordinate of a grid point on wall /* [15] */
yn = NODE_Y(node); // calculate y-coordinate of a grid point on wall
x0=0.0;
y0=0.0;
/* [20] */
r=sqrt(((xn-x0)*(xn-x0))+((yn-y0)*(yn-y0)));
theta=atan((yn-y0)/(xn-x0));
*omega=1000.0; /* [25] */
vel[0]=r*(*omega)*sin(theta);
vel[1]=-r*(*omega)*cos(theta);
} /* [30] */
}
end_f_loop(f,tf);
}

Any suggestions would be very much appreciated.

[usman naseer]

hi,,
i think it is not the problem of udf alone.It is possible that your udf is absolutely correct but you will still get this message.it is actually due to a combination of errors due to which Fluent can't proceed further.i will suggest you to check your boundary conditions and the values of pressure assigned.
Regards

[Allan Walsh]

If you do much with udfs, you may see this message a lot - starting all the way back from Version 4. I have not tried to look through your UDF code, but in general the error occurs when you try and access a variable that is not accessible. So you might look for something where the variable is not yet defined or you are overwriting something. Good luck.

[zzyan]

hi joe101
i have same problem about node_x(node), have you sloved this problem, if yes, could you tell me how ?
thanks

Originally Posted by Joe101

Hi,

I have written a UDF to rotate an ellipse in 2D with a constant angular velocity. It has been compiled and loaded without any errors. However, when i come to preview the mesh motion i get the following error message:

"Updating mesh at time level N...
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: ()"

I cant work out the problem but i have a feeling it might be my udf as i am new to c programming. Here is a copy of the udf:

#include "udf.h"
DEFINE_CG_MOTION(ellipse, dt, vel, omega, time, dtime)
{
face_t f;
Thread *tf = DT_THREAD(dt); /* [5] */
Node *node;
real xn, yn, r, theta, y0, x0;
int n;
begin_f_loop(f,tf) /* Loops over all faces in the thread passed in the DEFINE macro argument [10] */
{
f_node_loop(f,tf,node) /* Loops over all nodes in the face */
{
xn = NODE_X(node); // calculate x-coordinate of a grid point on wall /* [15] */
yn = NODE_Y(node); // calculate y-coordinate of a grid point on wall
x0=0.0;
y0=0.0;
/* [20] */
r=sqrt(((xn-x0)*(xn-x0))+((yn-y0)*(yn-y0)));
theta=atan((yn-y0)/(xn-x0));
*omega=1000.0; /* [25] */
vel[0]=r*(*omega)*sin(theta);
vel[1]=-r*(*omega)*cos(theta);
} /* [30] */
}
end_f_loop(f,tf);
}

Any suggestions would be very much appreciated.