Airfoil profile in CascadeStudio

[raydeleu]

This experiment shows how to create an airfoil profile in CascadeStudio. The code below contains two approaches:

• Using straight lines between the airfoil coordinates
• Using the BSplineTo method to force a curve through the airfoil coordinates

The second approach requires a small hack to make it work, namely starting the sketch at a position that is displaced by a small amount from the trailing edge of the profile. If the curve is started at the trailing edge two points are at the same location resulting in an error. An alternative would probably be to remove the first point from the data file.

As a third approach I tried to use a 3D spline through the airfoil coordinates. I then ran into the issue that I was not able to create a face from this wire. Without creating a face the extrusion of the airfoil yields a surface instead of a solid.

// chord, span and dihedral of the wing
let chord = 50;
let span  = 200;
let dihedral = 10; 

// the following array of points was created from a 
// standard airfoil coordinate data file
// the airfoil coordinate file is normalised to a standard chord of 1

let airfoilPoints=
[[1.0000000   ,0.0000000],
[0.9985383   ,0.0003261],
[0.9943357   ,0.0012896],
[0.9874835   ,0.0028991],
[0.9780353   ,0.0051591],
[0.9660390   ,0.0080639],
[0.9515443   ,0.0115947],
[0.9346057   ,0.0157195],
[0.9152843   ,0.0203926],
[0.8936495   ,0.0255547],
[0.8697794   ,0.0311333],
[0.8437625   ,0.0370433],
[0.8156986   ,0.0431884],
[0.7857000   ,0.0494617],
[0.7538929   ,0.0557483],
[0.7204180   ,0.0619265],
[0.6854321   ,0.0678706],
[0.6491079   ,0.0734536],
[0.6116358   ,0.0785498],
[0.5732228   ,0.0830380],
[0.5340930   ,0.0868053],
[0.4944863   ,0.0897496],
[0.4546574   ,0.0917838],
[0.4148737   ,0.0928383],
[0.3754127   ,0.0928639],
[0.3365591   ,0.0918344],
[0.2986011   ,0.0897478],
[0.2618267   ,0.0866279],
[0.2265198   ,0.0825240],
[0.1929555   ,0.0775104],
[0.1613969   ,0.0716848],
[0.1320908   ,0.0651660],
[0.1052651   ,0.0580905],
[0.0811259   ,0.0506086],
[0.0598565   ,0.0428803],
[0.0416163   ,0.0350696],
[0.0265420   ,0.0273396],
[0.0147495   ,0.0198457],
[0.0063383   ,0.0127275],
[0.0013965   ,0.0060949],
[0.0000000   ,0.0000000],
[0.0025589   ,-0.0060606],
[0.0092026   ,-0.0115698],
[0.0196689   ,-0.0165551],
[0.0336781   ,-0.0209976],
[0.0509521   ,-0.0248665],
[0.0712157   ,-0.0281356],
[0.0941973   ,-0.0307883],
[0.1196300   ,-0.0328200],
[0.1472530   ,-0.0342383],
[0.1768128   ,-0.0350618],
[0.2080639   ,-0.0353198],
[0.2407701   ,-0.0350502],
[0.2747044   ,-0.0342981],
[0.3096492   ,-0.0331148],
[0.3453962   ,-0.0315557],
[0.3817458   ,-0.0296795],
[0.4185066   ,-0.0275463],
[0.4554945   ,-0.0252170],
[0.4925323   ,-0.0227516],
[0.5294482   ,-0.0202088],
[0.5660754   ,-0.0176447],
[0.6022513   ,-0.0151121],
[0.6378161   ,-0.0126595],
[0.6726125   ,-0.0103308],
[0.7064852   ,-0.0081646],
[0.7392796   ,-0.0061931],
[0.7708424   ,-0.0044425],
[0.8010203   ,-0.0029317],
[0.8296603   ,-0.0016722],
[0.8566098   ,-0.0006682],
[0.8817164  ,0.0000844],
[0.9048280  ,0.0005973],
[0.9257939  ,0.0008906],
[0.9444642  ,0.0009917],
[0.9606910  ,0.0009361],
[0.9743280  ,0.0007659],
[0.9852307  ,0.0005300],
[0.9932535  ,0.0002828],
[0.9982433  ,0.0000842],
[1.0000000  ,0.0000000]]
let numberPoints = airfoilPoints.length

// scale the airfoil points to the chord length
let airfoilPointsLarge = airfoilPoints.map(function([x,y]){return [x*chord,y*chord]}) 

// create a sketch of the airfoil using straight lines
let airfoil = new Sketch([chord,0])
for (let i=0 ; i < (numberPoints); i++)
{
    airfoil.LineTo(airfoilPointsLarge[i]);
}
airfoil.End(true);

// create a sketch of the airfoil using a BSpline
// to make the BSpline work the starting point is moved 0.001 times the chord 
let airfoil2 = new Sketch([chord*(1.001),0])
airfoil2.BSplineTo(airfoilPointsLarge)
airfoil2.End(true)

let wing = Rotate([1,0,0],90-dihedral, Extrude(airfoil.Face(),[0,0,span]))
let wing2= Rotate([1,0,0],90+dihedral, Extrude(airfoil2.Face(),[0,0,-span]))

// Experiment to create a 3D spline along the airfoil coordinates
// let airfoilPointsLarge3D = []
// for (let j=0 ; j < numberPoints-1 ; j++)
// {
//     let x = airfoilPointsLarge[j+1][0]
//     let y = airfoilPointsLarge[j+1][1]
//     airfoilPointsLarge3D[j]=[x,y,0]
// }
// let path = BSpline(airfoilPointsLarge3D,true)
// let wing3 = Extrude(path.Face(),[0,0,200])
// issue: it seems not possible to create a face using path.Face()