naca-four-digit-airfoil

The equations for a NACA four-digit series airfoil

Introduction

NACA airfoils map a four digit code to an airfoil shape. For example, a '2412' airfoil is parsed to mean:

• The leading '2' indicates maximum camber is 2% of chord length
• The '4' indicates maximum camber is at 40% of the chord length
• The '12' indicates maximum thickness is 12% of the chord length

Live examples (change the query string to create your own):

• NACA 2412
• NACA 0012
• NACA 3418

Example

The code below calculates the x- and y-coordinates of the upper and lower surfaces, respectively, at 50% of the chord length.

var naca = require('naca-four-digit-airfoil')

naca('2412').evaluate(0.5)
// => [ 0.5005881887154037, 0.07238142883077964, 0.4994118112845963, -0.03349253994189075 ]

Installation

$ npm install naca-four-digit-airfoil

API

Based on NACA Code

require('naca-four-digit-airfoil')(nacaAirfoilCode[, chordLength = 1])

Parses the airfoil code and returns an object with functions that evaluate the shape of the airfoil for a unit chord length. Arguments are:

• nacaAirfoilCode: A four-digit string containing the NACA airfoil code. The first digit is the amount of camber in units of 1% of the chord length. The second digit is the location of maximum camber measured from the leading edge in units of 10% of the chord length. The final two digits are the thickness of the airfoil in units of 1% of the chord length.
• chordLength (optional, default = 1): The chord length of the airfoil.

The object returned contains the following functions:

• thickness: function(x): The half-thickness of the airfoil above or below the camber line at position x.
• camberLine: function(x): The height of the camber line above the centerline at position x.
• camberLineSlope: function(x): The slope of the camber line at position x.
• leadingEdgeRadius: function(): The radius of curvature of the leading edge.
• evaluate: function(x): The coordinates of the surface at position x. Returned in a four-element array containing coordinates [xUpper, yUpper, xLower, yLower]. The coordinates are calculated perpendicular to the line of camber. So that the x-coordinate of the surface at chord position x is slightly perturbed.
• xUpper: function(x): The x-coordinate of the upper surface of the airfoil.
• yUpper: function(x): The y-coordinate of the upper surface of the airfoil.
• xLower: function(x): The x-coordinate of the lower surface of the airfoil.
• yLower: function(x): The y-coordinate of the lower surface of the airfoil.

As Plain Functions

The functions are also available as unadorned functions accessible on the plain module. Using the variables defined above, they are:

• parse: function(code): Parse the four-character String airfoil code, returning m (the amount of camber as a fraction of chord length), p (the location of maximum camber as a fraction of chord length), and t (thickness as a fraction of chord length).
• thickness: function(x, c, t)
• camberLine: function(x, c, m, p)
• camberLineSlope: function(x, c, m, p)
• leadingEdgeRadius: function(t, c)
• xLower: function(x, c, m, p, t)
• xUpper: function(x, c, m, p, t)
• yLower: function(x, c, m, p, t)
• yUpper: function(x, c, m, p, t)
• evaluate: function(x, c, m, p, t)

License

© 2016 Ricky Reusser. MIT License.