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