# Aerofoil geometry - to spline or not?

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 July 2, 2003, 22:51 Aerofoil geometry - to spline or not? #1 Novak Elliott Guest   Posts: n/a 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.

 July 3, 2003, 08:14 Re: Aerofoil geometry - to spline or not? #2 Nicola Guest   Posts: n/a 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

 July 3, 2003, 09:20 Re: Aerofoil geometry - to spline or not? #3 Novak Elliott Guest   Posts: n/a 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.

 July 4, 2003, 13:16 Re: Aerofoil geometry - to spline or not? #4 James Date Guest   Posts: n/a Hi, Splines(natural) are good, so long as you don't over constrain them. Best to use as few points as necessary. Regards James

 July 9, 2003, 08:16 Re: Aerofoil geometry - to spline or not? #5 Alexey Guest   Posts: n/a 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

 April 17, 2011, 09:51 airfoil equation? #6 New Member   maryam Join Date: Apr 2011 Posts: 4 Rep Power: 7 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

 April 18, 2011, 09:48 #7 New Member   ivan Join Date: Jan 2010 Posts: 10 Rep Power: 8 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.

 April 18, 2011, 10:39 #8 New Member   maryam Join Date: Apr 2011 Posts: 4 Rep Power: 7 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.

 April 19, 2011, 03:10 #9 New Member   maryam Join Date: Apr 2011 Posts: 4 Rep Power: 7 I have another question, do u know a source for a gas turbine airfoil profile?

 April 20, 2011, 07:05 aieroil geometry #10 New Member   ivan Join Date: Jan 2010 Posts: 10 Rep Power: 8 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.

 April 21, 2011, 13:18 #11 New Member   maryam Join Date: Apr 2011 Posts: 4 Rep Power: 7 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

 April 28, 2011, 22:56 #12 Senior Member   Join Date: Nov 2009 Posts: 411 Rep Power: 11 @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. Do

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