Fluent UDF help!!!
 

Hi everyone

I am trying to model a moving sphere in hypersonic flow. I want the sphere to move according to the forces in experiences due to the incoming flow. It is a 2D axis symmetric case and hence i want the sphere to move in only one direction, basically 1 DOF motion. Below is my UDF, it complies alright, but when i try to run it fluent gives me a segmentation violation error, i am only defining my sphere as a rigid body in the zones with the UDF and have not defined anything else, i am using the smoothing parameter for my dynamic mesh. Any help will be much appreciated :)

#include "udf.h"
static real v_prev = 0.0;

DEFINE_CG_MOTION(sphere,dt,vel,omega,time,dtime)
{
Thread *t;
face_t f;
real NV_VEC(A);
real force, dv;

/* reset velocities */
NV_S(vel, =, 0.0);
NV_S(omega, =, 0.0);

if (!Data_Valid_P())
return;

/* get the thread pointer for which this motion is defined */
t = DT_THREAD(dt);

/* compute pressure force on body by looping through all faces */
force = 0.0;
begin_f_loop(f,t)
{
F_AREA(A,f,t);
force += F_P(f,t) * NV_MAG(A);
}
end_f_loop(f,t)

/* compute change in velocity, i.e., dv = F * dt / mass
velocity update using explicit Euler formula */
dv = dtime * force / .000756;
v_prev += dv;
Message ("time = %f, x_vel = %f, force = %f\n", time, v_prev,
force);

/* set x-component of velocity */
vel[0] = v_prev;
}