package net.sf.openrocket.aerodynamics.barrowman;
import static net.sf.openrocket.models.atmosphere.AtmosphericConditions.GAMMA;
import static net.sf.openrocket.util.MathUtil.pow2;
import net.sf.openrocket.aerodynamics.AerodynamicForces;
import net.sf.openrocket.aerodynamics.BarrowmanCalculator;
import net.sf.openrocket.aerodynamics.FlightConditions;
import net.sf.openrocket.aerodynamics.Warning;
import net.sf.openrocket.aerodynamics.WarningSet;
import net.sf.openrocket.rocketcomponent.BodyTube;
import net.sf.openrocket.rocketcomponent.RocketComponent;
import net.sf.openrocket.rocketcomponent.SymmetricComponent;
import net.sf.openrocket.rocketcomponent.Transition;
import net.sf.openrocket.util.BugException;
import net.sf.openrocket.util.Coordinate;
import net.sf.openrocket.util.LinearInterpolator;
import net.sf.openrocket.util.MathUtil;
import net.sf.openrocket.util.PolyInterpolator;
/**
* Calculates the aerodynamic properties of a <code>SymmetricComponent</code>.
* <p>
* CP and CNa are calculated by the Barrowman method extended to account for body lift
* by the method presented by Galejs. Supersonic CNa and CP are assumed to be the
* same as the subsonic values.
*
*
* @author Sampo Niskanen <sampo.niskanen@iki.fi>
*/
public class SymmetricComponentCalc extends RocketComponentCalc {
public static final double BODY_LIFT_K = 1.1;
private final double length;
private final double foreRadius, aftRadius;
private final double fineness;
private final Transition.Shape shape;
private final double param;
private final double frontalArea;
private final double fullVolume;
private final double planformArea, planformCenter;
private final double sinphi;
public SymmetricComponentCalc(RocketComponent c) {
super(c);
if (!(c instanceof SymmetricComponent)) {
throw new IllegalArgumentException("Illegal component type " + c);
}
SymmetricComponent component = (SymmetricComponent) c;
length = component.getLength();
foreRadius = component.getForeRadius();
aftRadius = component.getAftRadius();
fineness = length / (2 * Math.abs(aftRadius - foreRadius));
fullVolume = component.getFullVolume();
planformArea = component.getComponentPlanformArea();
planformCenter = component.getComponentPlanformCenter();
if (component instanceof BodyTube) {
shape = null;
param = 0;
frontalArea = 0;
sinphi = 0;
} else if (component instanceof Transition) {
shape = ((Transition) component).getType();
param = ((Transition) component).getShapeParameter();
frontalArea = Math.abs(Math.PI * (foreRadius * foreRadius - aftRadius * aftRadius));
double r = component.getRadius(0.99 * length);
sinphi = (aftRadius - r) / MathUtil.hypot(aftRadius - r, 0.01 * length);
} else {
throw new UnsupportedOperationException("Unknown component type " +
component.getComponentName());
}
}
private boolean isTube = false;
private double cnaCache = Double.NaN;
private double cpCache = Double.NaN;
/**
* Calculates the non-axial forces produced by the fins (normal and side forces,
* pitch, yaw and roll moments, CP position, CNa).
* <p>
* This method uses the Barrowman method for CP and CNa calculation and the
* extension presented by Galejs for the effect of body lift.
* <p>
* The CP and CNa at supersonic speeds are assumed to be the same as those at
* subsonic speeds.
*/
@Override
public void calculateNonaxialForces(FlightConditions conditions,
AerodynamicForces forces, WarningSet warnings) {
// Pre-calculate and store the results
if (Double.isNaN(cnaCache)) {
final double r0 = foreRadius;
final double r1 = aftRadius;
if (MathUtil.equals(r0, r1)) {
isTube = true;
cnaCache = 0;
} else {
isTube = false;
final double A0 = Math.PI * pow2(r0);
final double A1 = Math.PI * pow2(r1);
cnaCache = 2 * (A1 - A0);
// System.out.println("cnaCache = " + cnaCache);
cpCache = (length * A1 - fullVolume) / (A1 - A0);
}
}
Coordinate cp;
// If fore == aft, only body lift is encountered
if (isTube) {
cp = getLiftCP(conditions, warnings);
} else {
cp = new Coordinate(cpCache, 0, 0, cnaCache * conditions.getSincAOA() /
conditions.getRefArea()).average(getLiftCP(conditions, warnings));
}
forces.setCP(cp);
forces.setCNa(cp.weight);
forces.setCN(forces.getCNa() * conditions.getAOA());
forces.setCm(forces.getCN() * cp.x / conditions.getRefLength());
forces.setCroll(0);
forces.setCrollDamp(0);
forces.setCrollForce(0);
forces.setCside(0);
forces.setCyaw(0);
// Add warning on supersonic flight
if (conditions.getMach() > 1.1) {
warnings.add(Warning.SUPERSONIC);
}
}
/**
* Calculate the body lift effect according to Galejs.
*/
protected Coordinate getLiftCP(FlightConditions conditions, WarningSet warnings) {
/*
* Without this extra multiplier the rocket may become unstable at apogee
* when turning around, and begin oscillating horizontally. During the flight
* of the rocket this has no effect. It is effective only when AOA > 45 deg
* and the velocity is less than 15 m/s.
*
* TODO: MEDIUM: This causes an anomaly to the flight results with the CP jumping at apogee
*/
double mul = 1;
if ((conditions.getMach() < 0.05) && (conditions.getAOA() > Math.PI / 4)) {
mul = pow2(conditions.getMach() / 0.05);
}
return new Coordinate(planformCenter, 0, 0, mul * BODY_LIFT_K * planformArea / conditions.getRefArea() *
conditions.getSinAOA() * conditions.getSincAOA()); // sin(aoa)^2 / aoa
}
private LinearInterpolator interpolator = null;
@Override
public double calculatePressureDragForce(FlightConditions conditions,
double stagnationCD, double baseCD, WarningSet warnings) {
// Check for simple cases first
if (MathUtil.equals(foreRadius, aftRadius))
return 0;
if (length < 0.001) {
if (foreRadius < aftRadius) {
return stagnationCD * frontalArea / conditions.getRefArea();
} else {
return baseCD * frontalArea / conditions.getRefArea();
}
}
// Boattail drag computed directly from base drag
if (aftRadius < foreRadius) {
if (fineness >= 3)
return 0;
double cd = baseCD * frontalArea / conditions.getRefArea();
if (fineness <= 1)
return cd;
return cd * (3 - fineness) / 2;
}
// All nose cones and shoulders from pre-calculated and interpolating
if (interpolator == null) {
calculateNoseInterpolator();
}
return interpolator.getValue(conditions.getMach()) * frontalArea / conditions.getRefArea();
}
/*
* Experimental values of pressure drag for different nose cone shapes with a fineness
* ratio of 3. The data is taken from 'Collection of Zero-Lift Drag Data on Bodies
* of Revolution from Free-Flight Investigations', NASA TR-R-100, NTRS 19630004995,
* page 16.
*
* This data is extrapolated for other fineness ratios.
*/
private static final LinearInterpolator ellipsoidInterpolator = new LinearInterpolator(
new double[] { 1.2, 1.25, 1.3, 1.4, 1.6, 2.0, 2.4 },
new double[] { 0.110, 0.128, 0.140, 0.148, 0.152, 0.159, 0.162 /* constant */}
);
private static final LinearInterpolator x14Interpolator = new LinearInterpolator(
new double[] { 1.2, 1.3, 1.4, 1.6, 1.8, 2.2, 2.6, 3.0, 3.6 },
new double[] { 0.140, 0.156, 0.169, 0.192, 0.206, 0.227, 0.241, 0.249, 0.252 }
);
private static final LinearInterpolator x12Interpolator = new LinearInterpolator(
new double[] { 0.925, 0.95, 1.0, 1.05, 1.1, 1.2, 1.3, 1.7, 2.0 },
new double[] { 0, 0.014, 0.050, 0.060, 0.059, 0.081, 0.084, 0.085, 0.078 }
);
private static final LinearInterpolator x34Interpolator = new LinearInterpolator(
new double[] { 0.8, 0.9, 1.0, 1.06, 1.2, 1.4, 1.6, 2.0, 2.8, 3.4 },
new double[] { 0, 0.015, 0.078, 0.121, 0.110, 0.098, 0.090, 0.084, 0.078, 0.074 }
);
private static final LinearInterpolator vonKarmanInterpolator = new LinearInterpolator(
new double[] { 0.9, 0.95, 1.0, 1.05, 1.1, 1.2, 1.4, 1.6, 2.0, 3.0 },
new double[] { 0, 0.010, 0.027, 0.055, 0.070, 0.081, 0.095, 0.097, 0.091, 0.083 }
);
private static final LinearInterpolator lvHaackInterpolator = new LinearInterpolator(
new double[] { 0.9, 0.95, 1.0, 1.05, 1.1, 1.2, 1.4, 1.6, 2.0 },
new double[] { 0, 0.010, 0.024, 0.066, 0.084, 0.100, 0.114, 0.117, 0.113 }
);
private static final LinearInterpolator parabolicInterpolator = new LinearInterpolator(
new double[] { 0.95, 0.975, 1.0, 1.05, 1.1, 1.2, 1.4, 1.7 },
new double[] { 0, 0.016, 0.041, 0.092, 0.109, 0.119, 0.113, 0.108 }
);
private static final LinearInterpolator parabolic12Interpolator = new LinearInterpolator(
new double[] { 0.8, 0.9, 0.95, 1.0, 1.05, 1.1, 1.3, 1.5, 1.8 },
new double[] { 0, 0.016, 0.042, 0.100, 0.126, 0.125, 0.100, 0.090, 0.088 }
);
private static final LinearInterpolator parabolic34Interpolator = new LinearInterpolator(
new double[] { 0.9, 0.95, 1.0, 1.05, 1.1, 1.2, 1.4, 1.7 },
new double[] { 0, 0.023, 0.073, 0.098, 0.107, 0.106, 0.089, 0.082 }
);
private static final LinearInterpolator bluntInterpolator = new LinearInterpolator();
static {
for (double m = 0; m < 3; m += 0.05)
bluntInterpolator.addPoint(m, BarrowmanCalculator.calculateStagnationCD(m));
}
/**
* Calculate the LinearInterpolator 'interpolator'. After this call, if can be used
* to get the pressure drag coefficient at any Mach number.
*
* First, the transonic/supersonic region is computed. For conical and ogive shapes
* this is calculated directly. For other shapes, the values for fineness-ratio 3
* transitions are taken from the experimental values stored above (for parameterized
* shapes the values are interpolated between the parameter values). These are then
* extrapolated to the current fineness ratio.
*
* Finally, if the first data points in the interpolator are not zero, the subsonic
* region is interpolated in the form Cd = a*M^b + Cd(M=0).
*/
@SuppressWarnings("null")
private void calculateNoseInterpolator() {
LinearInterpolator int1 = null, int2 = null;
double p = 0;
interpolator = new LinearInterpolator();
/*
* Take into account nose cone shape. Conical and ogive generate the interpolator
* directly. Others store a interpolator for fineness ratio 3 into int1, or
* for parameterized shapes store the bounding fineness ratio 3 interpolators into
* int1 and int2 and set 0 <= p <= 1 according to the bounds.
*/
switch (shape) {
case CONICAL:
interpolator = calculateOgiveNoseInterpolator(0, sinphi); // param==0 -> conical
break;
case OGIVE:
interpolator = calculateOgiveNoseInterpolator(param, sinphi);
break;
case ELLIPSOID:
int1 = ellipsoidInterpolator;
break;
case POWER:
if (param <= 0.25) {
int1 = bluntInterpolator;
int2 = x14Interpolator;
p = param * 4;
} else if (param <= 0.5) {
int1 = x14Interpolator;
int2 = x12Interpolator;
p = (param - 0.25) * 4;
} else if (param <= 0.75) {
int1 = x12Interpolator;
int2 = x34Interpolator;
p = (param - 0.5) * 4;
} else {
int1 = x34Interpolator;
int2 = calculateOgiveNoseInterpolator(0, 1 / MathUtil.safeSqrt(1 + 4 * pow2(fineness)));
p = (param - 0.75) * 4;
}
break;
case PARABOLIC:
if (param <= 0.5) {
int1 = calculateOgiveNoseInterpolator(0, 1 / MathUtil.safeSqrt(1 + 4 * pow2(fineness)));
int2 = parabolic12Interpolator;
p = param * 2;
} else if (param <= 0.75) {
int1 = parabolic12Interpolator;
int2 = parabolic34Interpolator;
p = (param - 0.5) * 4;
} else {
int1 = parabolic34Interpolator;
int2 = parabolicInterpolator;
p = (param - 0.75) * 4;
}
break;
case HAACK:
int1 = vonKarmanInterpolator;
int2 = lvHaackInterpolator;
p = param * 3;
break;
default:
throw new UnsupportedOperationException("Unknown transition shape: " + shape);
}
if (p < 0 || p > 1.00001) {
throw new BugException("Inconsistent parameter value p=" + p + " shape=" + shape);
}
// Check for parameterized shape and interpolate if necessary
if (int2 != null) {
LinearInterpolator int3 = new LinearInterpolator();
for (double m : int1.getXPoints()) {
int3.addPoint(m, p * int2.getValue(m) + (1 - p) * int1.getValue(m));
}
for (double m : int2.getXPoints()) {
int3.addPoint(m, p * int2.getValue(m) + (1 - p) * int1.getValue(m));
}
int1 = int3;
}
// Extrapolate for fineness ratio if necessary
if (int1 != null) {
double log4 = Math.log(fineness + 1) / Math.log(4);
for (double m : int1.getXPoints()) {
double stag = bluntInterpolator.getValue(m);
interpolator.addPoint(m, stag * Math.pow(int1.getValue(m) / stag, log4));
}
}
/*
* Now the transonic/supersonic region is ok. We still need to interpolate
* the subsonic region, if the values are non-zero.
*/
double min = interpolator.getXPoints()[0];
double minValue = interpolator.getValue(min);
if (minValue < 0.001) {
// No interpolation necessary
return;
}
double cdMach0 = 0.8 * pow2(sinphi);
double minDeriv = (interpolator.getValue(min + 0.01) - minValue) / 0.01;
// These should not occur, but might cause havoc for the interpolation
if ((cdMach0 >= minValue - 0.01) || (minDeriv <= 0.01)) {
return;
}
// Cd = a*M^b + cdMach0
double a = minValue - cdMach0;
double b = minDeriv / a;
for (double m = 0; m < minValue; m += 0.05) {
interpolator.addPoint(m, a * Math.pow(m, b) + cdMach0);
}
}
private static final PolyInterpolator conicalPolyInterpolator =
new PolyInterpolator(new double[] { 1.0, 1.3 }, new double[] { 1.0, 1.3 });
private static LinearInterpolator calculateOgiveNoseInterpolator(double param,
double sinphi) {
LinearInterpolator interpolator = new LinearInterpolator();
// In the range M = 1 ... 1.3 use polynomial approximation
double cdMach1 = 2.1 * pow2(sinphi) + 0.6019 * sinphi;
double[] poly = conicalPolyInterpolator.interpolator(
1.0 * sinphi, cdMach1,
4 / (GAMMA + 1) * (1 - 0.5 * cdMach1), -1.1341 * sinphi
);
// Shape parameter multiplier
double mul = 0.72 * pow2(param - 0.5) + 0.82;
for (double m = 1; m < 1.3001; m += 0.02) {
interpolator.addPoint(m, mul * PolyInterpolator.eval(m, poly));
}
// Above M = 1.3 use direct formula
for (double m = 1.32; m < 4; m += 0.02) {
interpolator.addPoint(m, mul * (2.1 * pow2(sinphi) + 0.5 * sinphi / MathUtil.safeSqrt(m * m - 1)));
}
return interpolator;
}
}