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Old   March 1, 2012, 10:27
Default Airfoil Pitching
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sheth roh
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Hi,

I am performing airfoil Pitching in fluent.

The pitching is simple harmonic and is about the centroid. From diagram you can see that pitcing is about z axis.

Here is my udf

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

DEFINE_CG_MOTION(pitch, dt, vel, omega, time, dtime)
{
real ampl,omg,count;
/* motion */
ampl = 0.7 ; /* amplitude of rotation in radians */
omg = 150; /* angular frequency */

omega [2] = ampl * sin (omg * time);
}
The problem is that I dont see any oscillation happening. The Cl curve also remains constant with time.

Can you tell whats wrong with code. ?

Note: I only set dynamic mesh zone in airfoil(So DO I need to set other zones too?)


I have tried setting 6 DOF on and off but in both case it doesnt work.
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Old   March 9, 2012, 10:26
Smile Airfoil Pitching Problem
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Saif Ullah
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You should add following commands to the udf. Don't use omega[2] simply. I hope it will work. Set only your airfoil as dynamic zone and give CG absolute coordinates in creating dynamic zones. You airfoil should start rotating about that point.

daft = (60 * (pi/180)) * 2*pi*0.2 * sin(2*pi*0.2 * time);
alpha = 60 * cos(2*pi*0.2 * time);
/* set omega */
omega[2] = daft;

Regards
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Old   March 11, 2012, 03:17
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sheth roh
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Quote:
Originally Posted by saifullahkhalid View Post
You should add following commands to the udf. Don't use omega[2] simply. I hope it will work. Set only your airfoil as dynamic zone and give CG absolute coordinates in creating dynamic zones. You airfoil should start rotating about that point.

daft = (60 * (pi/180)) * 2*pi*0.2 * sin(2*pi*0.2 * time);
alpha = 60 * cos(2*pi*0.2 * time);
/* set omega */
omega[2] = daft;

Regards
Hey Thanks for reply.

I will definitely try this code. Meanwhile can you please tell me if the following setting are correct for dynamic mesh:

- I am giving motion via define_cg_motion
- I set moving zone only to the airfoil, I consider it rigid and provide motion via udf. SO DO I NEED TO SET OUTER REGION AS DEFORMING
- I set only smoothing and remshing not layering.
- Also when I use prism mesh around airfoil, it always gives negative volume. SO for such mesh what settings should be made.

I really appreciate your help.

Regards
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