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April 7, 2011, 09:01 
creating lines normal to airfoil surface

#1 
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Irfan
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Hi,
Does anyone knows how to draw lines normal to airfoil surface in CFXPost? I am simulating an airfoil in CFX and I need lines normal to airfoil surface to determine some parameters? Irfan 

July 15, 2011, 09:28 

#2 
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I'd really like to know this!


July 17, 2011, 08:03 

#3 
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Hi,
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. 

July 17, 2011, 10:37 

#4 
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Irfan
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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. 

July 18, 2011, 08:58 

#5 
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Pick a point on the airfoi; use the values of "Normal X", "Normal Y" and "Normal Z" in CFDPost to calculate the location of a point normal to the surface; join the two points to make a line.


July 19, 2011, 11:23 

#6 
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Joshua Counsil
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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. 

July 20, 2011, 06:40 

#7 
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What about if there is no equation or datapoints 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 CFDPost to get the aerofoil shape at the spanwise position of choice. 

Tags 
airfoil, cfx post 
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