creating lines normal to airfoil surface

iffy · April 7, 2011, 10:01

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

bash0r · July 15, 2011, 10:28

I'd really like to know this!

Abou ali · July 17, 2011, 09:03

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.

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.

April 7, 2011, 10:01	creating lines normal to airfoil surface	#1
iffy 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

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
How do I compute the normal vector to a surface with FEM	Vasilis	Main CFD Forum	3	July 31, 2009 08:59
creating airfoil geometry using ICEM CFD	jaber	Main CFD Forum	1	November 2, 2007 17:26
Creating inflation layers for elbow with airfoil !	Aplus	CFX	1	March 13, 2006 23:22
creating volume from a surface file for CFD	Amir	Main CFD Forum	0	December 24, 2002 03:08
CFX4.3 -build analysis form	Chie Min	CFX	5	July 13, 2001 00:19

July 15, 2011, 10:28		#2
bash0r New Member Join Date: Apr 2011 Posts: 12 Rep Power: 15	I'd really like to know this!

July 17, 2011, 09:03		#3
Abou ali Member Join Date: Nov 2009 Posts: 49 Rep Power: 17	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: P1P2P1PN = 0 -where denote the scalar product-, this equation permits you to find any points (Pn) from the normal line.

July 17, 2011, 11:37		#4
iffy 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, 09:58		#5
stumpy 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, 12:23		#6
Josh Senior Member Joshua Counsil Join Date: Jul 2009 Location: Halifax, Nova Scotia, Canada Posts: 366 Rep Power: 18	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, 07:40		#7
siw Senior Member Stuart Join Date: Jul 2009 Location: Portsmouth, England Posts: 739 Rep Power: 26	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.