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sinusoidal airfoil oscillations

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Old   August 3, 2017, 07:00
Default sinusoidal airfoil oscillations
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flanag
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Hi everyone!

I am studying 2D transient dynamic stall on a s809 as part of my masters and I was hoping for your assistance. I am using this formula to control the oscillations:

alpha(t)=alpha(0)+alpha(1)sin(2*pi*f*t). where alpha(0)=mean angle 8deg;

alpha(1)=5.5deg oscillation amplitude; f=1.2Hz; Ufreestream=30m/s

I have used the following interpreted udf and added it to the inner rotating domain under mesh motion.

#include <stdio.h>
#include <math.h>
#include "udf.h"

DEFINE_CG_MOTION(airfoil_pitch, dt, vel, omega, time, dtime)
{
real pitchampl, pitchdispl, omg, pi, count;

pi = 3.14159265;


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

/* motion */
pitchampl = 5.5 * pi / 180; /* angular pitch amplitude */
omg = 2 * pi * 1.2; /* angular frequency */
pitchdispl = pitchampl * sin(omg * time); /* resultant displacement */

omega[2] = pitchampl * omg * cos(omg * time);
}
However this wont take into account the mean angle, has anyone done something similar. if this udf is correct perhaps i am inputting it incorrectly in the fluent gui.

so should i define the freestream at the inlet with respect to that mean angle ; Components >> x_vel=30cos8 and y_vel=30 sin8.

Also, how could i find what the angle of attack is for each time step?

Thanks in advance for any help.

P.S. If you would prefer to contact me via email instead of this thread please contact me at flanagl1@tcd.ie.
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Old   August 4, 2017, 10:42
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flanag
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Has anyone done something similar with dynamic stall modelling on an airfoil using fluent, do i also need to set a sinusThank youoidal osillating freestream?
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