git.gag.com Git - debian/openrocket/blob - src/net/sf/openrocket/aerodynamics/ConeDragTest.java

   1 package net.sf.openrocket.aerodynamics;
   2
   3 import net.sf.openrocket.util.PolyInterpolator;
   4
   5 public class ConeDragTest {
   6
   7         private static final double DELTA = 0.01;
   8         private static final double SUBSONIC = 0.0;
   9         private static final double SUPERSONIC = 1.3;
  10
  11
  12         private static final PolyInterpolator polyInt2 = new PolyInterpolator(
  13                         new double[] {1.0, SUPERSONIC}
  14                         ,new double[] {1.0, SUPERSONIC}
  15                         ,new double[] {SUPERSONIC}
  16         );
  17
  18         private final double angle;
  19         private final double sin;
  20         private final double ratio;
  21
  22         private final double[] int2;
  23
  24         // Coefficients for subsonic interpolation  a * M^b + c
  25         private final double a, b, c;
  26
  27
  28
  29         public ConeDragTest(double angle) {
  30                 this.angle = angle;
  31                 this.sin = Math.sin(angle);
  32                 this.ratio = 1.0 / (2*Math.tan(angle));
  33
  34                 double dsuper = (supersonic(SUPERSONIC+DELTA) - supersonic(SUPERSONIC))/DELTA;
  35
  36
  37                 c = subsonic(0);
  38                 a = sonic() - c;
  39                 b = sonicDerivative() / a;
  40
  41
  42                 int2 = polyInt2.interpolator(
  43                                 sonic(), supersonic(SUPERSONIC)
  44                                 , sonicDerivative(), dsuper
  45                                 ,0
  46                 );
  47
  48                 System.err.println("At mach1: CD="+sin+" dCD/dM="+(4.0/2.4*(1-0.5*sin)));
  49
  50         }
  51
  52         private double subsonic(double m) {
  53                 return 0.8*sin*sin/Math.sqrt(1-m*m);
  54         }
  55
  56         private double sonic() {
  57                 return sin;
  58         }
  59
  60         private double sonicDerivative() {
  61                 return 4.0/2.4*(1-0.5*sin);
  62         }
  63
  64         private double supersonic(double m) {
  65                 return 2.1 * sin*sin + 0.5*sin/Math.sqrt(m*m-1);
  66         }
  67
  68
  69
  70
  71         public double getCD(double m) {
  72                 if (m >= SUPERSONIC)
  73                         return supersonic(m);
  74
  75                 if (m <= 1.0)
  76                         return a * Math.pow(m,b) + c;
  77                 return PolyInterpolator.eval(m, int2);
  78
  79 //              return PolyInterpolator.eval(m, interpolator);
  80         }
  81
  82
  83
  84         public static void main(String[] arg) {
  85
  86                 ConeDragTest cone10 = new ConeDragTest(10.0*Math.PI/180);
  87                 ConeDragTest cone20 = new ConeDragTest(20.0*Math.PI/180);
  88                 ConeDragTest cone30 = new ConeDragTest(30.0*Math.PI/180);
  89
  90                 ConeDragTest coneX = new ConeDragTest(5.0*Math.PI/180);
  91
  92                 for (double m=0; m < 4.0001; m+=0.02) {
  93                         System.out.println(m + " "
  94                                         + cone10.getCD(m) + " "
  95                                         + cone20.getCD(m) + " "
  96                                         + cone30.getCD(m) + " "
  97 //                                      + coneX.getCD(m)
  98                         );
  99                 }
 100
 101         }
 102
 103 }