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Use UDF to change the attack angle of flow over 3D wing

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Old   May 3, 2013, 03:07
Default Use UDF to change the attack angle of flow over 3D wing
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nguyen van trieu
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Hi everyone,

I am a new with ANSYS FLUENT. I am doing simulation with the flow over 3Dwing (NACA0012). I want to change the attack angle by using UDF. Could anyone teach me how to use the UDF for this case?
thanks you!

Xavier
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Old   May 3, 2013, 03:34
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Are you studying the pitching motion of the wing or you simply want to study the flow at several angles of attack?
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Old   May 3, 2013, 05:55
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Hi,
if it just the angle of attack which you want to change, you can do it directly by changing the x and y component of velocity in the velocity inlent boundary condition.
If you want to learn to do it in udf you have to do the same by writing this component inside a small c program..
this is an example of how the inlet velocity is changed according to the y distance to get a profile

http://combust.hit.edu.cn:8080/fluen...udf/node61.htm
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Old   May 3, 2013, 14:42
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You can also do it in workbench
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Old   May 15, 2013, 01:07
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Hi everyone,

Thanks to all of you!
@blackmask: I am not going to simulate for pitching motion, only do simulation for some AoA.
@Ananthakrishnan:
Because the wing is located in the virtual wind tunnel, is it ok when I change the AoA by change the Vx, Vy components?
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Old   May 15, 2013, 05:22
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No, its not going to pose any serious threat..There will be some difference in magnitude of result between the two. But you will not be misguided..In brief, if there is a increase in lift then there will always be an increase whether you change the components of velocity or if you change the wing AOA. If you want a very very very precise result, later you can continue by changing the AOA. I suggest you to get an idea of whats happening by changing the components and then "if required" change the AOA
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Old   May 15, 2013, 23:12
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Thanks Ananthakrishnan,

As I understand, for this case of fluid domain, the inlet bc is a straight line. This is different compare with the semi-circle (C-shape) as many people used. So I think that for every AoA we should change the geometry rather than change the velocity components. Because the top and the bottom are wall, they are not velocity inlet.
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Old   June 14, 2013, 03:37
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sir Ananthakrishnan
i am doing a similar type of simulation
but whet i set inlet velocity at certain angle of attack
i get the flow accumulated at upper surface of wind tunnel
giving uneven flow throughout the wind tunnel ( higher velocity at upper surface of wind tunnel and lower velocity at lower surface of wind tunnel)
and i have chosen boundary conditions as symmetry for both upper and lower surface of wind tunnel
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