# sinusoidal airfoil oscillations

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August 3, 2017, 07:00
sinusoidal airfoil oscillations
#1
New Member

flanag
Join Date: Jun 2017
Posts: 8
Rep Power: 2
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.

Attached Images
 mesh1.PNG (61.8 KB, 4 views) mesh2.PNG (114.2 KB, 4 views) cell zone conditon.PNG (47.2 KB, 4 views)

 August 4, 2017, 10:42 #2 New Member   flanag Join Date: Jun 2017 Posts: 8 Rep Power: 2 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?

 Tags airfoil pitching 2d

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