# creating lines normal to airfoil surface

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 April 7, 2011, 09:01 creating lines normal to airfoil surface #1 New Member   Irfan Join Date: Jan 2011 Location: Netherlands Posts: 16 Rep Power: 15 Hi, 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? Irfan

 July 15, 2011, 09:28 #2 New Member   Join Date: Apr 2011 Posts: 12 Rep Power: 15 I'd really like to know this!

 July 17, 2011, 08:03 #3 Member   Join Date: Nov 2009 Posts: 49 Rep Power: 16 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 New Member   Irfan Join Date: Jan 2011 Location: Netherlands Posts: 16 Rep Power: 15 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 Senior Member   Join Date: Apr 2009 Posts: 531 Rep Power: 21 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.

 July 19, 2011, 11:23 #6 Senior Member   Joshua Counsil Join Date: Jul 2009 Location: Halifax, Nova Scotia, Canada Posts: 366 Rep Power: 17 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 Senior Member   Stuart Join Date: Jul 2009 Location: Portsmouth, England Posts: 733 Rep Power: 25 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.

 Tags airfoil, cfx post