# Airfoil Pitching

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March 1, 2012, 10:27
Airfoil Pitching
#1
Member

sheth roh
Join Date: Jul 2011
Posts: 56
Rep Power: 6
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 #include #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.
Attached Images
 fluent.jpg (102.4 KB, 36 views)

 March 9, 2012, 10:26 Airfoil Pitching Problem #2 New Member   Saif Ullah Join Date: Aug 2011 Posts: 5 Rep Power: 6 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

March 11, 2012, 03:17
#3
Member

sheth roh
Join Date: Jul 2011
Posts: 56
Rep Power: 6
Quote:
 Originally Posted by saifullahkhalid 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

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.

Regards

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