libs/Threading/Naca4.scad@15eac37578b7 (annotated)
libs/Threading/Naca4.scad
Wed, 12 Sep 2018 12:48:28 +0200
- author
- mdd
- date
- Wed, 12 Sep 2018 12:48:28 +0200
- changeset 0
- 15eac37578b7
- permissions
- -rw-r--r--
initial commit of FluidSwitch prototype
| 0 | 1 | // Naca4.scad - library for parametric airfoils of 4 digit NACA series |
| 2 | // Code: Rudolf Huttary, Berlin | |
| 3 | // June 2015 | |
| 4 | // commercial use prohibited | |
| 5 | ||
| 6 | ||
| 7 | // general use: for more examples refer to sampler.scad | |
| 8 | // naca = naca digits or 3el vector (default = 12 or [0, 0, .12]) | |
| 9 | // L = chord length [mm] (default= 100) | |
| 10 | // N = # sample points (default= 81) | |
| 11 | // h = height [mm] (default= 1) | |
| 12 | // open = close at the thin end? (default = true) | |
| 13 | // two equivalent example calls | |
| 14 | airfoil(naca = 2408, L = 60, N=1001, h = 30, open = false); | |
| 15 | // airfoil(naca = [.2, .4, .32], L = 60, N=1001, h = 30, open = false); | |
| 16 | ||
| 17 | module help() | |
| 18 | { | |
| 19 | echo(str("\n\nList of signatures in lib:\n=================\n", | |
| 20 | "module airfoil(naca=2412, L = 100, N = 81, h = 1, open = false) - renders airfoil object\n", | |
| 21 | "module airfoil(naca=[.2, .4, .12], L = 100, N = 81, h = 1, open = false) - renders airfoil object using percentage for camber, camber distance and thicknes\n", | |
| 22 | "function airfoil_data(naca=12, L = 100, N = 81, open = false)\n", | |
| 23 | "=================\n")); | |
| 24 | } | |
| 25 | ||
| 26 | help(); | |
| 27 | // this is the object | |
| 28 | module airfoil(naca=12, L = 100, N = 81, h = 1, open = false) | |
| 29 | { | |
| 30 | linear_extrude(height = h) | |
| 31 | polygon(points = airfoil_data(naca, L, N, open)); | |
| 32 | } | |
| 33 | ||
| 34 | // this is the main function providing the airfoil data | |
| 35 | function airfoil_data(naca=12, L = 100, N = 81, open = false) = | |
| 36 | let(Na = len(naca)!=3?NACA(naca):naca) | |
| 37 | let(A = [.2969, -0.126, -.3516, .2843, open?-0.1015:-0.1036]) | |
| 38 | [for (b=[-180:360/(N):179.99]) | |
| 39 | let (x = (1-cos(b))/2) | |
| 40 | let(yt = sign(b)*Na[2]/.2*(A*[sqrt(x), x, x*x, x*x*x, x*x*x*x])) | |
| 41 | Na[0]==0?L*[x, yt]:L*camber(x, yt, Na[0], Na[1], sign(b))]; | |
| 42 | ||
| 43 | // helper functions | |
| 44 | function NACA(naca) = | |
| 45 | let (M = floor(naca/1000)) | |
| 46 | let (P = floor((naca-M*1000)/100)) | |
| 47 | [M/100, P/10, floor(naca-M*1000-P*100)/100]; | |
| 48 | ||
| 49 | function camber(x, y, M, P, upper) = | |
| 50 | let(yc = (x<P)?M/P/P*(2*P*x-x*x): M/(1-P)/(1-P)*(1 - 2*P + 2*P*x -x*x)) | |
| 51 | let(dy = (x<P)?2*M/P/P*(P-x):2*M/(1-P)/(1-P)*(P-x)) | |
| 52 | let(th = atan(dy)) | |
| 53 | [upper ? x - y*sin(th):x + y*sin(th), upper ? yc + y*cos(th):yc - y*cos(th)]; | |
| 54 | ||
| 55 |
