[shahriar omee]

hi

i am trying to simulate a vertical axis wind turbine which has 3 blades with flap attached to it.For simultaneous flapping and rotating motion i used the UDF below. Found it in the forum.Used it for a primary trial.

I compiled it properly and seems to be working good but in display zone motion i see different motion for different CG location. I hooked the UDF to the flap which is rigid body.For CG location X=0, Y=0 the flap seems to only rotate about the axis. For CG location X=0,Y=0.3 (which is the radius of rotor) the body is flapping but not rotating.What should be done to get both the flapping and rotation at the same time?

Any kind of help and suggestion regarding the UDF is highly appreciated.

TIA
Omee


#include "udf.h"

DEFINE_CG_MOTION(wing, dt, vel, omega, time, dtime)
{
real a1, a2, thxdot, thydot, thzdot, w, pi, thx, thy;

pi = 3.141592654;

/* define motion variables */
a1 = 30 * pi / 180; /* 30 degree flapping amplitude */
a2 = 30 * pi / 180; /* 30 degree feathering amplitude */
w = 2 * pi * 25; /* 25 Hz frequency */

/* define motion in reference axes */
thx = DT_THETA (dt)[1] * pi/180; /* flapping angle - set by orientation macro DT_THETA */
thy = DT_THETA (dt)[2] * pi/180; /* feathering angle - set by orientation macro DT_THETA */
thxdot = 0; /* flapping speed */
thydot = a2 * w * sin(w*time); /* feathering speed */
thzdot = - a1 * w * cos(w*time); /* yawing (spinning) speed */

/* define wing rotational motion in body coordinates */
omega[0] = 0;
omega[1] = thydot * cos(thx) + thzdot * cos(thy) * sin(thx);
omega[2] = thzdot * cos(thy) * cos(thx) - thydot * sin(thx);
}