
[Sponsors] 
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: 7 
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 
New Member
Join Date: Apr 2011
Posts: 12
Rep Power: 7 
I'd really like to know this!


July 17, 2011, 08:03 

#3 
Member
Join Date: Nov 2009
Posts: 49
Rep Power: 8 
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: 7 
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: 530
Rep Power: 13 
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 
Senior Member
Joshua Counsil
Join Date: Jul 2009
Location: Halifax, Nova Scotia, Canada
Posts: 366
Rep Power: 10 
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: 472
Rep Power: 15 
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 
Thread Tools  
Display Modes  


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 07:59 
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 12, 2001 23:19 