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

   1 package net.sf.openrocket.aerodynamics.barrowman;
   2
   3 import static net.sf.openrocket.models.atmosphere.AtmosphericConditions.GAMMA;
   4 import static net.sf.openrocket.util.MathUtil.pow2;
   5 import net.sf.openrocket.aerodynamics.AerodynamicForces;
   6 import net.sf.openrocket.aerodynamics.BarrowmanCalculator;
   7 import net.sf.openrocket.aerodynamics.FlightConditions;
   8 import net.sf.openrocket.aerodynamics.WarningSet;
   9 import net.sf.openrocket.rocketcomponent.BodyTube;
  10 import net.sf.openrocket.rocketcomponent.RocketComponent;
  11 import net.sf.openrocket.rocketcomponent.SymmetricComponent;
  12 import net.sf.openrocket.rocketcomponent.Transition;
  13 import net.sf.openrocket.util.BugException;
  14 import net.sf.openrocket.util.Coordinate;
  15 import net.sf.openrocket.util.LinearInterpolator;
  16 import net.sf.openrocket.util.MathUtil;
  17 import net.sf.openrocket.util.PolyInterpolator;
  18
  19
  20
  21 /**
  22  * Calculates the aerodynamic properties of a <code>SymmetricComponent</code>.
  23  * <p>
  24  * CP and CNa are calculated by the Barrowman method extended to account for body lift
  25  * by the method presented by Galejs.  Supersonic CNa and CP are assumed to be the
  26  * same as the subsonic values.
  27  *
  28  *
  29  * @author Sampo Niskanen <sampo.niskanen@iki.fi>
  30  */
  31 public class SymmetricComponentCalc extends RocketComponentCalc {
  32
  33         public static final double BODY_LIFT_K = 1.1;
  34
  35         private final SymmetricComponent component;
  36
  37         private final double length;
  38         private final double r1, r2;
  39         private final double fineness;
  40         private final Transition.Shape shape;
  41         private final double param;
  42         private final double area;
  43
  44         public SymmetricComponentCalc(RocketComponent c) {
  45                 super(c);
  46                 if (!(c instanceof SymmetricComponent)) {
  47                         throw new IllegalArgumentException("Illegal component type " + c);
  48                 }
  49                 this.component = (SymmetricComponent) c;
  50
  51
  52                 length = component.getLength();
  53                 r1 = component.getForeRadius();
  54                 r2 = component.getAftRadius();
  55
  56                 fineness = length / (2 * Math.abs(r2 - r1));
  57
  58                 if (component instanceof BodyTube) {
  59                         shape = null;
  60                         param = 0;
  61                         area = 0;
  62                 } else if (component instanceof Transition) {
  63                         shape = ((Transition) component).getType();
  64                         param = ((Transition) component).getShapeParameter();
  65                         area = Math.abs(Math.PI * (r1 * r1 - r2 * r2));
  66                 } else {
  67                         throw new UnsupportedOperationException("Unknown component type " +
  68                                         component.getComponentName());
  69                 }
  70         }
  71
  72
  73         private boolean isTube = false;
  74         private double cnaCache = Double.NaN;
  75         private double cpCache = Double.NaN;
  76
  77
  78         /**
  79          * Calculates the non-axial forces produced by the fins (normal and side forces,
  80          * pitch, yaw and roll moments, CP position, CNa).
  81          * <p>
  82          * This method uses the Barrowman method for CP and CNa calculation and the
  83          * extension presented by Galejs for the effect of body lift.
  84          * <p>
  85          * The CP and CNa at supersonic speeds are assumed to be the same as those at
  86          * subsonic speeds.
  87          */
  88         @Override
  89         public void calculateNonaxialForces(FlightConditions conditions,
  90                         AerodynamicForces forces, WarningSet warnings) {
  91
  92                 // Pre-calculate and store the results
  93                 if (Double.isNaN(cnaCache)) {
  94                         final double r0 = component.getForeRadius();
  95                         final double r1 = component.getAftRadius();
  96
  97                         if (MathUtil.equals(r0, r1)) {
  98                                 isTube = true;
  99                                 cnaCache = 0;
 100                         } else {
 101                                 isTube = false;
 102
 103                                 final double A0 = Math.PI * pow2(r0);
 104                                 final double A1 = Math.PI * pow2(r1);
 105
 106                                 cnaCache = 2 * (A1 - A0);
 107                                 System.out.println("cnaCache = " + cnaCache);
 108                                 cpCache = (component.getLength() * A1 - component.getFullVolume()) / (A1 - A0);
 109                         }
 110                 }
 111
 112                 Coordinate cp;
 113
 114                 // If fore == aft, only body lift is encountered
 115                 if (isTube) {
 116                         cp = getLiftCP(conditions, warnings);
 117                 } else {
 118                         cp = new Coordinate(cpCache, 0, 0, cnaCache * conditions.getSincAOA() /
 119                                         conditions.getRefArea()).average(getLiftCP(conditions, warnings));
 120                 }
 121
 122                 forces.setCP(cp);
 123                 forces.setCNa(cp.weight);
 124                 forces.setCN(forces.getCNa() * conditions.getAOA());
 125                 forces.setCm(forces.getCN() * cp.x / conditions.getRefLength());
 126                 forces.setCroll(0);
 127                 forces.setCrollDamp(0);
 128                 forces.setCrollForce(0);
 129                 forces.setCside(0);
 130                 forces.setCyaw(0);
 131
 132
 133                 // Add warning on supersonic flight
 134                 if (conditions.getMach() > 1.1) {
 135                         warnings.add("Body calculations may not be entirely accurate at supersonic speeds.");
 136                 }
 137
 138         }
 139
 140
 141
 142         /**
 143          * Calculate the body lift effect according to Galejs.
 144          */
 145         protected Coordinate getLiftCP(FlightConditions conditions, WarningSet warnings) {
 146                 double area = component.getComponentPlanformArea();
 147                 double center = component.getComponentPlanformCenter();
 148
 149                 /*
 150                  * Without this extra multiplier the rocket may become unstable at apogee
 151                  * when turning around, and begin oscillating horizontally.  During the flight
 152                  * of the rocket this has no effect.  It is effective only when AOA > 45 deg
 153                  * and the velocity is less than 15 m/s.
 154                  *
 155                  * TODO: MEDIUM:  This causes an anomaly to the flight results with the CP jumping at apogee
 156                  */
 157                 double mul = 1;
 158                 if ((conditions.getMach() < 0.05) && (conditions.getAOA() > Math.PI / 4)) {
 159                         mul = pow2(conditions.getMach() / 0.05);
 160                 }
 161
 162                 return new Coordinate(center, 0, 0, mul * BODY_LIFT_K * area / conditions.getRefArea() *
 163                                 conditions.getSinAOA() * conditions.getSincAOA()); // sin(aoa)^2 / aoa
 164         }
 165
 166
 167
 168         private LinearInterpolator interpolator = null;
 169
 170         @Override
 171         public double calculatePressureDragForce(FlightConditions conditions,
 172                         double stagnationCD, double baseCD, WarningSet warnings) {
 173
 174                 if (component instanceof BodyTube)
 175                         return 0;
 176
 177                 if (!(component instanceof Transition)) {
 178                         throw new BugException("Pressure calculation of unknown type: " +
 179                                         component.getComponentName());
 180                 }
 181
 182                 // Check for simple cases first
 183                 if (r1 == r2)
 184                         return 0;
 185
 186                 if (length < 0.001) {
 187                         if (r1 < r2) {
 188                                 return stagnationCD * area / conditions.getRefArea();
 189                         } else {
 190                                 return baseCD * area / conditions.getRefArea();
 191                         }
 192                 }
 193
 194
 195                 // Boattail drag computed directly from base drag
 196                 if (r2 < r1) {
 197                         if (fineness >= 3)
 198                                 return 0;
 199                         double cd = baseCD * area / conditions.getRefArea();
 200                         if (fineness <= 1)
 201                                 return cd;
 202                         return cd * (3 - fineness) / 2;
 203                 }
 204
 205
 206                 // All nose cones and shoulders from pre-calculated and interpolating
 207                 if (interpolator == null) {
 208                         calculateNoseInterpolator();
 209                 }
 210
 211                 return interpolator.getValue(conditions.getMach()) * area / conditions.getRefArea();
 212         }
 213
 214
 215
 216         /*
 217          * Experimental values of pressure drag for different nose cone shapes with a fineness
 218          * ratio of 3.  The data is taken from 'Collection of Zero-Lift Drag Data on Bodies
 219          * of Revolution from Free-Flight Investigations', NASA TR-R-100, NTRS 19630004995,
 220          * page 16.
 221          *
 222          * This data is extrapolated for other fineness ratios.
 223          */
 224
 225         private static final LinearInterpolator ellipsoidInterpolator = new LinearInterpolator(
 226                         new double[] { 1.2, 1.25, 1.3, 1.4, 1.6, 2.0, 2.4 },
 227                         new double[] { 0.110, 0.128, 0.140, 0.148, 0.152, 0.159, 0.162 /* constant */}
 228                         );
 229         private static final LinearInterpolator x14Interpolator = new LinearInterpolator(
 230                         new double[] { 1.2, 1.3, 1.4, 1.6, 1.8, 2.2, 2.6, 3.0, 3.6 },
 231                         new double[] { 0.140, 0.156, 0.169, 0.192, 0.206, 0.227, 0.241, 0.249, 0.252 }
 232                         );
 233         private static final LinearInterpolator x12Interpolator = new LinearInterpolator(
 234                         new double[] { 0.925, 0.95, 1.0, 1.05, 1.1, 1.2, 1.3, 1.7, 2.0 },
 235                         new double[] { 0, 0.014, 0.050, 0.060, 0.059, 0.081, 0.084, 0.085, 0.078 }
 236                         );
 237         private static final LinearInterpolator x34Interpolator = new LinearInterpolator(
 238                         new double[] { 0.8, 0.9, 1.0, 1.06, 1.2, 1.4, 1.6, 2.0, 2.8, 3.4 },
 239                         new double[] { 0, 0.015, 0.078, 0.121, 0.110, 0.098, 0.090, 0.084, 0.078, 0.074 }
 240                         );
 241         private static final LinearInterpolator vonKarmanInterpolator = new LinearInterpolator(
 242                         new double[] { 0.9, 0.95, 1.0, 1.05, 1.1, 1.2, 1.4, 1.6, 2.0, 3.0 },
 243                         new double[] { 0, 0.010, 0.027, 0.055, 0.070, 0.081, 0.095, 0.097, 0.091, 0.083 }
 244                         );
 245         private static final LinearInterpolator lvHaackInterpolator = new LinearInterpolator(
 246                         new double[] { 0.9, 0.95, 1.0, 1.05, 1.1, 1.2, 1.4, 1.6, 2.0 },
 247                         new double[] { 0, 0.010, 0.024, 0.066, 0.084, 0.100, 0.114, 0.117, 0.113 }
 248                         );
 249         private static final LinearInterpolator parabolicInterpolator = new LinearInterpolator(
 250                         new double[] { 0.95, 0.975, 1.0, 1.05, 1.1, 1.2, 1.4, 1.7 },
 251                         new double[] { 0, 0.016, 0.041, 0.092, 0.109, 0.119, 0.113, 0.108 }
 252                         );
 253         private static final LinearInterpolator parabolic12Interpolator = new LinearInterpolator(
 254                         new double[] { 0.8, 0.9, 0.95, 1.0, 1.05, 1.1, 1.3, 1.5, 1.8 },
 255                         new double[] { 0, 0.016, 0.042, 0.100, 0.126, 0.125, 0.100, 0.090, 0.088 }
 256                         );
 257         private static final LinearInterpolator parabolic34Interpolator = new LinearInterpolator(
 258                         new double[] { 0.9, 0.95, 1.0, 1.05, 1.1, 1.2, 1.4, 1.7 },
 259                         new double[] { 0, 0.023, 0.073, 0.098, 0.107, 0.106, 0.089, 0.082 }
 260                         );
 261         private static final LinearInterpolator bluntInterpolator = new LinearInterpolator();
 262         static {
 263                 for (double m = 0; m < 3; m += 0.05)
 264                         bluntInterpolator.addPoint(m, BarrowmanCalculator.calculateStagnationCD(m));
 265         }
 266
 267         /**
 268          * Calculate the LinearInterpolator 'interpolator'.  After this call, if can be used
 269          * to get the pressure drag coefficient at any Mach number.
 270          *
 271          * First, the transonic/supersonic region is computed.  For conical and ogive shapes
 272          * this is calculated directly.  For other shapes, the values for fineness-ratio 3
 273          * transitions are taken from the experimental values stored above (for parameterized
 274          * shapes the values are interpolated between the parameter values).  These are then
 275          * extrapolated to the current fineness ratio.
 276          *
 277          * Finally, if the first data points in the interpolator are not zero, the subsonic
 278          * region is interpolated in the form   Cd = a*M^b + Cd(M=0).
 279          */
 280         @SuppressWarnings("null")
 281         private void calculateNoseInterpolator() {
 282                 LinearInterpolator int1 = null, int2 = null;
 283                 double p = 0;
 284
 285                 interpolator = new LinearInterpolator();
 286
 287                 double r = component.getRadius(0.99 * length);
 288                 double sinphi = (r2 - r) / MathUtil.hypot(r2 - r, 0.01 * length);
 289
 290                 /*
 291                  * Take into account nose cone shape.  Conical and ogive generate the interpolator
 292                  * directly.  Others store a interpolator for fineness ratio 3 into int1, or
 293                  * for parameterized shapes store the bounding fineness ratio 3 interpolators into
 294                  * int1 and int2 and set 0 <= p <= 1 according to the bounds.
 295                  */
 296                 switch (shape) {
 297                 case CONICAL:
 298                         interpolator = calculateOgiveNoseInterpolator(0, sinphi); // param==0 -> conical
 299                         break;
 300
 301                 case OGIVE:
 302                         interpolator = calculateOgiveNoseInterpolator(param, sinphi);
 303                         break;
 304
 305                 case ELLIPSOID:
 306                         int1 = ellipsoidInterpolator;
 307                         break;
 308
 309                 case POWER:
 310                         if (param <= 0.25) {
 311                                 int1 = bluntInterpolator;
 312                                 int2 = x14Interpolator;
 313                                 p = param * 4;
 314                         } else if (param <= 0.5) {
 315                                 int1 = x14Interpolator;
 316                                 int2 = x12Interpolator;
 317                                 p = (param - 0.25) * 4;
 318                         } else if (param <= 0.75) {
 319                                 int1 = x12Interpolator;
 320                                 int2 = x34Interpolator;
 321                                 p = (param - 0.5) * 4;
 322                         } else {
 323                                 int1 = x34Interpolator;
 324                                 int2 = calculateOgiveNoseInterpolator(0, 1 / Math.sqrt(1 + 4 * pow2(fineness)));
 325                                 p = (param - 0.75) * 4;
 326                         }
 327                         break;
 328
 329                 case PARABOLIC:
 330                         if (param <= 0.5) {
 331                                 int1 = calculateOgiveNoseInterpolator(0, 1 / Math.sqrt(1 + 4 * pow2(fineness)));
 332                                 int2 = parabolic12Interpolator;
 333                                 p = param * 2;
 334                         } else if (param <= 0.75) {
 335                                 int1 = parabolic12Interpolator;
 336                                 int2 = parabolic34Interpolator;
 337                                 p = (param - 0.5) * 4;
 338                         } else {
 339                                 int1 = parabolic34Interpolator;
 340                                 int2 = parabolicInterpolator;
 341                                 p = (param - 0.75) * 4;
 342                         }
 343                         break;
 344
 345                 case HAACK:
 346                         int1 = vonKarmanInterpolator;
 347                         int2 = lvHaackInterpolator;
 348                         p = param * 3;
 349                         break;
 350
 351                 default:
 352                         throw new UnsupportedOperationException("Unknown transition shape: " + shape);
 353                 }
 354
 355                 if (p < 0 || p > 1.00001) {
 356                         throw new BugException("Inconsistent parameter value p=" + p + " shape=" + shape);
 357                 }
 358
 359
 360                 // Check for parameterized shape and interpolate if necessary
 361                 if (int2 != null) {
 362                         LinearInterpolator int3 = new LinearInterpolator();
 363                         for (double m : int1.getXPoints()) {
 364                                 int3.addPoint(m, p * int2.getValue(m) + (1 - p) * int1.getValue(m));
 365                         }
 366                         for (double m : int2.getXPoints()) {
 367                                 int3.addPoint(m, p * int2.getValue(m) + (1 - p) * int1.getValue(m));
 368                         }
 369                         int1 = int3;
 370                 }
 371
 372                 // Extrapolate for fineness ratio if necessary
 373                 if (int1 != null) {
 374                         double log4 = Math.log(fineness + 1) / Math.log(4);
 375                         for (double m : int1.getXPoints()) {
 376                                 double stag = bluntInterpolator.getValue(m);
 377                                 interpolator.addPoint(m, stag * Math.pow(int1.getValue(m) / stag, log4));
 378                         }
 379                 }
 380
 381
 382                 /*
 383                  * Now the transonic/supersonic region is ok.  We still need to interpolate
 384                  * the subsonic region, if the values are non-zero.
 385                  */
 386
 387                 double min = interpolator.getXPoints()[0];
 388                 double minValue = interpolator.getValue(min);
 389                 if (minValue < 0.001) {
 390                         // No interpolation necessary
 391                         return;
 392                 }
 393
 394                 double cdMach0 = 0.8 * pow2(sinphi);
 395                 double minDeriv = (interpolator.getValue(min + 0.01) - minValue) / 0.01;
 396
 397                 // These should not occur, but might cause havoc for the interpolation
 398                 if ((cdMach0 >= minValue - 0.01) || (minDeriv <= 0.01)) {
 399                         return;
 400                 }
 401
 402                 // Cd = a*M^b + cdMach0
 403                 double a = minValue - cdMach0;
 404                 double b = minDeriv / a;
 405
 406                 for (double m = 0; m < minValue; m += 0.05) {
 407                         interpolator.addPoint(m, a * Math.pow(m, b) + cdMach0);
 408                 }
 409         }
 410
 411
 412         private static final PolyInterpolator conicalPolyInterpolator =
 413                         new PolyInterpolator(new double[] { 1.0, 1.3 }, new double[] { 1.0, 1.3 });
 414
 415         private static LinearInterpolator calculateOgiveNoseInterpolator(double param,
 416                         double sinphi) {
 417                 LinearInterpolator interpolator = new LinearInterpolator();
 418
 419                 // In the range M = 1 ... 1.3 use polynomial approximation
 420                 double cdMach1 = 2.1 * pow2(sinphi) + 0.6019 * sinphi;
 421
 422                 double[] poly = conicalPolyInterpolator.interpolator(
 423                                 1.0 * sinphi, cdMach1,
 424                                 4 / (GAMMA + 1) * (1 - 0.5 * cdMach1), -1.1341 * sinphi
 425                                 );
 426
 427                 // Shape parameter multiplier
 428                 double mul = 0.72 * pow2(param - 0.5) + 0.82;
 429
 430                 for (double m = 1; m < 1.3001; m += 0.02) {
 431                         interpolator.addPoint(m, mul * PolyInterpolator.eval(m, poly));
 432                 }
 433
 434                 // Above M = 1.3 use direct formula
 435                 for (double m = 1.32; m < 4; m += 0.02) {
 436                         interpolator.addPoint(m, mul * (2.1 * pow2(sinphi) + 0.5 * sinphi / Math.sqrt(m * m - 1)));
 437                 }
 438
 439                 return interpolator;
 440         }
 441
 442
 443
 444 }