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Old   December 31, 2015, 23:10
Default 3D Wing Analysis
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Erdem Eskioglu
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Hello,

I'm analysing a 3D wing in FLUENT with inviscid model. Basic geometry of the wing is:
Chord=0.133 m
Span=0.540 m
Airfoil= NACA 0015
Freestream Velocity= 37.19 m/s

I need to analyse the wing at varying angle of attack from -14 to 14 with 2 degree steps.
Geometry is made in CATIA exported to ANSYS meshed, and solved in FLUENT.
However I get lower lift coefficient than the wind tunnel results.
I checked the reference values, force vectors, mesh, made it finer increased the fluid domain size, tried adapt function in FLUENT but no luck still I'm getting lower lift coefficient for example:
CL in Windtunnel at 6 degree Angle of Atack = 0.7085
CL in FLUENT at 6 degree Angle of Attack = 0.53
Why is this happening?
Can someone help me to solve this problem? I can send you the case and data files for you to see what I am doing wrong.

Best regards,
Erdem
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Old   January 2, 2016, 19:03
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Why inviscid? No viscous forces?
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Old   January 2, 2016, 19:08
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Because I want to do an inviscid analysis at first. Also I'm having high skewness at the trailing edge when I use "inflation" in ansys meshing to obtain boundary layer mesh.
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Old   January 2, 2016, 21:19
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Quote:
Originally Posted by ErdemEskioglu View Post
Because I want to do an inviscid analysis at first. Also I'm having high skewness at the trailing edge when I use "inflation" in ansys meshing to obtain boundary layer mesh.
Couple of questions again:

1) Is viscous forces negligible in the wind tunnel results you are referring to? If then your approach is okay.

2) Is it a blunt trailing edge? or a sharp one? Because depending on this the meshing strategy will change.

Here are some general hints;

To get right CL drop down your Y+ to 1, Increase no of mesh elements, Use the correct turbulence model ( k-omega SST mostly used for aerospace) ...

Avoiding high skewness is tricky. It can be done though.
Is it a C type domain you are using? Or a sphere type?
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Old   January 2, 2016, 21:33
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1) For the CL it can be negligible in no-stall region angle of attack.

2) It is sharp trailing edge and that is the main cause of skewness I guess. Cells coming from top and bottom sides of surface are trying to merge in trailing edge and it causes skewness.

I increased no of mesh elements(reducing size of elements) especially at airfoil at the part close to the trailing edge and trailing edge line itself but it does not give any solution to skewness.

I thought a baffle face at the trailing edge point and extending to the downstream field would prevent merging the cells at TE. But I couldn't figure out how could I create and mesh that baffle face in ANSYS Meshing.
Apart from that I don't know what should be done to avoid skewness

A box domain is what I am using. Surfaces far from the wing placed inside.

Regards
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Old   January 2, 2016, 22:27
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All right. Put the files in a drop box or some sharing website and inbox me the link or something. I would have preferred if it was made in ICEM though but anyways I will have a look.

Or if you wanna share in public then it's okay too.



Regards

Shereez
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