comparison: libs/Threading/Naca4.scad
libs/Threading/Naca4.scad
- changeset 0
- 15eac37578b7
equal
deleted
inserted
replaced
| -1:000000000000 | 0:15eac37578b7 |
|---|---|
| 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 |
