Equation curves

[PiotrekL1]

Hi

I found tutorial for symmetrical equation curve for NACA Airfouil in Inventor 2013. http://www.youtube.com/watch?v=zKSBe9hImTE

I need to create assymentric airfoil. I am wondering if there is a possibility to put equation in Inventor which looks like the one I attached in doc file.

If it is not possible that's OK as I can use coordinate generator in the internet and put coordinates into inventor so I can draw it but It would be nice to put set of the equations rather than manually put 100 points. 

I know that those equations are more complicated and I don't know how to start with them in Inventor

[pcrawley]

I'm not in front of Inventor right now, so can't check the syntax for the equation curve editor - but I would say "yes", this is possible.  For now, I'd just recommend inserting points from Excel.  Inventor will draw a spline through the imported points for you - it's like the poor-mans Equation curve editor!  Have a look at the expanded tool-tip for the format of the Excel sheet.  (It's on the Sketch > Insert panel.)

[PiotrekL1 · Accepted solution]

Hi

I will follow your advise. I will generate coordinates in the NACA tool and put then through MS Excel into inventor

Thank you very much

[hanson.alex]

Been working on this to...

My end goal is to have an assembly with n number of NACA 4 digit (and others) profiles. This will allow the user to quickly develop a surface model to export to a CFD program.

Parameters to control (between each section):

• Sweep
• sweep
• dihedral angle
• span
• twist

Parameters to control (For each section):

• NACA Type
• NACA Parameters
• Camber length

Step 1: Developing NACA 4 digit profiles

Approach 1: Sketch Equation Curve

Following equitation on http://en.wikipedia.org/wiki/NACA_airfoil, I was successfully able to develop the mean camber line (with two different equation curves). While trying to add the equations for the top and bottom of the profile, I ran into many issues most of which resolved after time, although not all.

Problem(s):

1.  The parametric equations are not fixed in space (i.e.. you can drag them around) and I have not been able to successfully relate all 6 curves, trailing edge, and leading edge (approx. as a circle).
2. The beginning of the forward curves approach div by zero and are as such not useful.
3. Very cumbersome, extremely hard to use and error prone.

Approach 2: Thickness Circles + mean camber line = Spline (kinda)

Using my sucsessful mean camber line, I added 10 circles along the mean camber line and demendsioned their linear poisiton along the mean cambber line using the x_u parametric equations, and their heigth demension from the x-axis using the y_u parametric equations.

Problem(s):

1. After passing the max mean camber position, things started going badly. It turns out that inventor was not parsing the equations correctly. This could be a program or user error, the jury is out on that one. See post here: http://forums.autodesk.com/t5/Autodesk-Inventor/Demension-Copy-Parse-Error/m-p/3920847 
2. Cumbersome (seeing a trend here). While I could type all the equation in the tiny window and get it work corretly, I feel I have better things to do in my life, and there is probably a better approach.

Propossed Approach 1: iRule/iLogic/API

The title is garbled because I don't know enough about each of those, but my preliminary research shows this may be the correct approach. The plan is to create a set of point using the parametric equations to define a spline.

If anyone has any questions/comments/advise please let me know.

[mda2249]

stumbled here a bunch of times while trying to solve this same issue. here's what I got future inventor NACA 4 digit problem solvers:

download octave. the free version of matlab.

run this script: (which I found onine and modified for me 🙂 

___________________________

%octave script airfoil

clear all
clc
c=1; %put yo chord length here
s=num2str(4424); %put yo digits here
NACA=s; %4 digits
d1=str2double(s(1)); % pulls the first digit out of the scalar
d2=str2double(s(2));% pulls the second digit out of the scalar
d34=str2double(s(3:4)); % pulls the third and fourth digit out of the scalar
m=d1/100;
p=d2/10;
t=d34/100;
x=linspace(0, c, 500);
yt =5*t*c*(.2969*(sqrt(x/c))+-.1260*(x/c)+-.3516*(x/c).^2+.2843*(x/c).^3+-.1015*(x/c).^4);
for k = 1:length(x)
if x(k) <= p*c
yc(k)=m*(x(k)/p^2)*(2*p-(x(k)/c));
dx(k)=(2*m)/p^2*(p-(x(k)/c));
elseif x(k) > p*c
yc(k)=m*((c-x(k))/(1-p)^2)*(1+(x(k)/c)-(2*p));
dx(k)=((2*m)/(1-p)^2)*(p-(x(k)/c));
end
%upper and lower limits of the airfoil (xu,yu) ; (xl,yl)
theta=atan(dx(k));
xu(k)=x(k)-yt(k)*sin(theta);
yu(k)=yc(k)+yt(k)*cos(theta);
xl(k)=x(k)+yt(k)*sin(theta);
yl(k)=yc(k)-yt(k)*cos(theta);
end
%plot of airfoil
plot(xu,yu)
hold on
plot(xl,yl,'r')
plot(x,yc,'g')
axis equal

cd("C:/Users/Marlon Alessandra/Desktop/Marlon's files/Octave/airfoil")   %put yor path to save the file here the quotations sometimes give an error so try mod them first

d=[xu xl];
e=[yu yl];
f=[d;e];

dlmwrite('airfoil_matrix.txt',f',':')

_________________________

A) modify script values to reflect the NACA values.

b) modify script for where to save the points.

.... now you can place the file in excel.. the dilimieaters are : and ;