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iffy April 7, 2011 10:01

creating lines normal to airfoil surface
Does anyone knows how to draw lines normal to airfoil surface in CFX-Post? I am simulating an airfoil in CFX and I need lines normal to airfoil surface to determine some parameters?


bash0r July 15, 2011 10:28

I'd really like to know this!

Abou ali July 17, 2011 09:03

This is a mathematical problem. If you want to create a line
normal to the airfoil at a specific point P1, you must first,
calculate a vector tangent to the airfoil by using the nearest
point (P2) to P1 then if we assume that the normal line passe by
P1 and a point Pn (x, y) we can find the equation of the normal by:
P1P2*P1PN = 0
-where * denote the scalar product-, this equation permits you to
find any points (Pn) from the normal line.

iffy July 17, 2011 11:37

Abou Ali thanks for your reply.
This way to create normal line works if equation for the airfoil is available which is not always the case. But how to determine tangent if equation is not available.

stumpy July 18, 2011 09:58

Pick a point on the airfoi; use the values of "Normal X", "Normal Y" and "Normal Z" in CFD-Post to calculate the location of a point normal to the surface; join the two points to make a line.

Josh July 19, 2011 12:23

If the airfoil is described by an equation, e.g., the NACA series of airfoils, then you can you the negative inverse slope of that equation at each desired point to find the normal lines.

If the airfoil cannot be described by a single equation, import the points into a spreadsheet processor, e.g., Excel, and break the airfoil into several equations.

siw July 20, 2011 07:40

What about if there is no equation or data-points for the aerofoil?

I'm trying to do the same but only have an IGES file of a wing (for a 3D simulation) I then use a Plane and Polyline in CFD-Post to get the aerofoil shape at the spanwise position of choice.

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