[el123]

Hi there,

I'm trying to create a UDF to make a circular domain rotate about its centre but constrained to between its starting position and -90 degrees. Once it reaches -90 degrees I want it to rotate the back the opposite way to its start position.

I have differentiated theta = -90*(sin(100t))^2 to get theta dot (angular speed)

I currently have the below UDF that doesn't seem to be constraining the motion:

#include "udf.h"
#define PI 3.141592654
real theta_max = - 90 * (PI/180);
real omega = 100 * (2 * PI/60);

DEFINE_TRANSIENT_PROFILE(circ, time)
{
real theta_dot = 2 * theta_max * omega * cos(omega * time) * sin(omega * time);
return theta_dot;

}

Thanks in advance.

[AlexanderZ]

you code should work without issues
however, I prefer to make few changes to avoid using standard names

#include "udf.h"
real theta_max = - 90 * (M_PI/180);
real omega_w = 100 * (2 * M_PI/60);

DEFINE_TRANSIENT_PROFILE(circ, time)
{
real theta_dot = 2 * theta_max * omega_w * cos(omega_w * time) * sin(omega_w * time);
return theta_dot;
}

use small enough time step. Seems like the period of wave is about 0.4 sec