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Aerofoil geometry - to spline or not?

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Old   July 2, 2003, 22:51
Default Aerofoil geometry - to spline or not?
  #1
Novak Elliott
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Hi everyone,

I'm going to be looking at flow over a streamlined body, not too dissimilar to an aerofoil except that it isn't designed for lift but instead to minimise drag. I have an equation for the cross-sectional curves but I'm not sure of the best way to generate the geometry. A curve must be approximated by a finite number of points and the choices available are either a spline fit which uses polynomials or a linear fit which involves simply joining all of the points with straight lines. I can ensure vertical tangency at the leading edge using either approach but I'm not sure which method is most appropriate. Both of these curve approximations will affect the boundary layer and separation point.

Any suggestions?

Novak.
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Old   July 3, 2003, 08:14
Default Re: Aerofoil geometry - to spline or not?
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Nicola
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You can use Bezier curves. I don't know the details, but it seems the leading approach used in parametric airfoil generation.

Hope it helps

Nicola
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Old   July 3, 2003, 09:20
Default Re: Aerofoil geometry - to spline or not?
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Novak Elliott
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After thinking about it I agree. By using a Bezier curve fit the resulting mesh surface will be more consistent across varying numbers of mesh seeds than if a linear fit was used. The package I'm using has 3rd order polynomial Beziers so that should suffice.

Cheers, Novak.
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Old   July 4, 2003, 13:16
Default Re: Aerofoil geometry - to spline or not?
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James Date
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Hi,

Splines(natural) are good, so long as you don't over constrain them. Best to use as few points as necessary.

Regards James
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Old   July 9, 2003, 08:16
Default Re: Aerofoil geometry - to spline or not?
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Alexey
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Also you can use multilevel B-splines, see paper

http://www.postech.ac.kr/~leesy/ftp/tvcg97.pdf

They are simple and work very well and fast.

Alexey
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Old   April 17, 2011, 09:51
Default airfoil equation?
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maryam
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Hi
Can I have some points of an airfoil curvature, in fact I need an equation foa an airfoil shape for my fortran code, thank u so much if u can help me how to find this equation.
maryam
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Old   April 18, 2011, 09:48
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ivan
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Hello,

you can use Hicks Henne function, Parsec, Bspline or Class-Shape-Transformation.
Parces : http://www.as.dlr.de/hs/d.PARSEC/Parsec.html
CST : AIAA-96013.pdf
...
HH : CastonguayNadarajah-2007-0059.ppt
I have question, do You want to optimize airfoil.

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Old   April 18, 2011, 10:39
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maryam
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no, I just want to do a heat transformation project, there is no optimization on the airfoil shape.
thank u very much for your answer.
I have another question, do u know a source for a gas turbine airfoil profile?

Last edited by maryam_mirza; April 19, 2011 at 03:13.
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Old   April 19, 2011, 03:10
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I have another question, do u know a source for a gas turbine airfoil profile?
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Old   April 20, 2011, 07:05
Default aieroil geometry
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ivan
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Hello,

I asked my proffesor, but he didn't kwon it. I found a paper Differential Evolution in Aerodynamic Optimization.
ceteseerx
10.1.1.35.6925
In this paper, the optimization of turbine airfoil is decribed.

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Old   April 21, 2011, 13:18
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maryam
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thank u very much, but an optimized equation isn't a necessity for me. I just need an equation in Cartesian or any other coordinate, that's all!
thanks
maryam
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Old   April 28, 2011, 22:56
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@maryam

A simple approach will be to use a least square approximation in order to obtain a polynomial equation for your points. You can use Matlab for this, or if you are in a hurry just send me the points of your airfoil and I'll send you the equation.

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