[AfreedFaizan]

I'm working on oscillating airfoils based on flapping wings. In order to do so, I took a simple airfoil and made the geometry. I had no issues while building the "udflib" and the code which I used given below. Once I set the CG location and preview the motion. It is rotating 360 degs at a very fast rpm rather than executing slow shm. I'm pretty sure it's something to do with the software rather than the code. Please help me because this is my uni project.

#include "udf.h"
#define Freq 5 % defining flapping frequency i.e 5, 6, 7, 8, 9 and 10Hz
#define PI 22/7
#define angular_freq 2.0*PI*Freq % defining angular frequency
#define tetmax 30.0*PI/180 % defining angular amplitude
DEFINE_CG_MOTION (shm, dt, cg_vel, cg_omega, time, dtime)
{
real omega;
omega = tetmax *angular_freq* cos (angular_freq *time);
cg_vel[0] = 0.0;
cg_vel[1] = 0.0;
cg_vel[2] = 0.0;
cg_omega[0] = 0.0;
cg_omega[1] = 0.0;
cg_omega[2] = omega;
}

[bored_bot]

hey any fixes? im facing the exact same issue.

[bored_bot]

#define PI 22/7
#define angular_freq 2.0*PI*Freq % defining angular frequency
#define tetmax 30.0*PI/180 % defining angular amplitude

You could try the following things:
1) change the PI macro definition, instead of that you invoke M_PI instead
2) the reason it rotates instead of executing a simple harmonic motion is because the angles are inconsistent.

so here's the fixed code:

#define angular_freq 2.0*Freq*M_PI/180
#define tetmax 30.0*PI/180

Hope this fixed your code!