I've simulated a pitching motion in Ansys Fluent with UDF, a CG_MOTION mocro.The domain is supposed to oscillate but it rotates,judging by animation. The motion is not a pitching one.
DEFINE_CG_MOTION(airfoil, dt, vel, omega, time, dtime)
{
Thread *t;
face_t f;
real NV_VEC(A);
real 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 change in velocity, i.e., dv = F * dt / mass
velocity update using explicit Euler formula */
dv = 1.89+0.75 * sin( 0.37 * dtime);
v_prev += dv;
Message("time = %f, x_vel = %f, force = %f\n", time, v_prev);
/* set x-component of velocity */
vel[2] = v_prev;
}
what would be the problem?
If u are referring to Electrical grid with number of generators in clusters at some distance from each other, the electrical oscillation occur both intra cluster and inter cluster. The frequency is between .7 to 2 HZ and low to be noticed in wave forms. When a mass spring model is disturbed by a single frequency and single inertia forcing funcion the oscillations are predictable. In an actual grid the forcing functions are at different frequencies an d inertia . Hence you may not see the pitching.
Not sure if it answers.
Thanks Ashok for ur answer. Actually I haven t got what you said. I know the answer now, I used the wrong UDF. I should define the angular velocity in the the UDF not the velocity.
I had not clearly understood the question, Thanks you have got yr ans. Yes , angular velocity makes sense.
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