This file wasn't ever supposed to committed
This commit is contained in:
JoePfeiffer
parent
265a6e0b7b
commit
5d8a95d0a2
@ -1,710 +0,0 @@
|
||||
package net.sf.openrocket.aerodynamics.barrowman;
|
||||
|
||||
import static java.lang.Math.pow;
|
||||
import static net.sf.openrocket.util.MathUtil.pow2;
|
||||
|
||||
import java.util.Arrays;
|
||||
|
||||
import net.sf.openrocket.aerodynamics.AerodynamicForces;
|
||||
import net.sf.openrocket.aerodynamics.FlightConditions;
|
||||
import net.sf.openrocket.aerodynamics.Warning;
|
||||
import net.sf.openrocket.aerodynamics.Warning.Other;
|
||||
import net.sf.openrocket.aerodynamics.WarningSet;
|
||||
import net.sf.openrocket.rocketcomponent.BodyTube;
|
||||
import net.sf.openrocket.rocketcomponent.FinSet;
|
||||
import net.sf.openrocket.rocketcomponent.RocketComponent;
|
||||
import net.sf.openrocket.rocketcomponent.TubeFinSet;
|
||||
import net.sf.openrocket.util.Coordinate;
|
||||
import net.sf.openrocket.util.LinearInterpolator;
|
||||
import net.sf.openrocket.util.MathUtil;
|
||||
import net.sf.openrocket.util.PolyInterpolator;
|
||||
import net.sf.openrocket.util.Transformation;
|
||||
|
||||
import org.slf4j.Logger;
|
||||
import org.slf4j.LoggerFactory;
|
||||
|
||||
/**
|
||||
* Preliminary computation of tube fin aerodynamics.
|
||||
*
|
||||
* Uses a complete clone of FinSetCalc modelling each tube fin as 3 individual fins. It does not correctly account for
|
||||
* fin & tube fin interference.
|
||||
*
|
||||
* Changes to BarrowmanCalculator's calculateFrictionDrag are also probably required.
|
||||
*
|
||||
* @author kruland
|
||||
*
|
||||
*/
|
||||
public class TubeFinSetCalc extends LaunchLugCalc {
|
||||
|
||||
private final static Logger log = LoggerFactory.getLogger(FinSetCalc.class);
|
||||
|
||||
private static final double STALL_ANGLE = (20 * Math.PI / 180);
|
||||
|
||||
/** Number of divisions in the fin chords. */
|
||||
protected static final int DIVISIONS = 48;
|
||||
|
||||
protected double macLength = Double.NaN; // MAC length
|
||||
protected double macLead = Double.NaN; // MAC leading edge position
|
||||
protected double macSpan = Double.NaN; // MAC spanwise position
|
||||
protected double finArea = Double.NaN; // Fin area
|
||||
protected double ar = Double.NaN; // Fin aspect ratio
|
||||
protected double span = Double.NaN; // Fin span
|
||||
protected double cosGamma = Double.NaN; // Cosine of midchord sweep angle
|
||||
protected double cosGammaLead = Double.NaN; // Cosine of leading edge sweep angle
|
||||
protected double rollSum = Double.NaN; // Roll damping sum term
|
||||
|
||||
|
||||
protected double[] chordLead = new double[DIVISIONS];
|
||||
protected double[] chordTrail = new double[DIVISIONS];
|
||||
protected double[] chordLength = new double[DIVISIONS];
|
||||
|
||||
private final double[] poly = new double[6];
|
||||
|
||||
private final double thickness;
|
||||
private final double bodyRadius;
|
||||
private final int finCount;
|
||||
private final double baseRotation;
|
||||
private final double cantAngle;
|
||||
protected final int interferenceFinCount;
|
||||
private final FinSet.CrossSection crossSection;
|
||||
|
||||
private final TubeFinSet tubeFinSet;
|
||||
|
||||
public TubeFinSetCalc(RocketComponent component) {
|
||||
super(component);
|
||||
if (!(component instanceof TubeFinSet)) {
|
||||
throw new IllegalArgumentException("Illegal component type " + component);
|
||||
}
|
||||
|
||||
tubeFinSet = (TubeFinSet) component;
|
||||
final TubeFinSet fin = (TubeFinSet) component;
|
||||
|
||||
thickness = fin.getThickness();
|
||||
bodyRadius = fin.getBodyRadius();
|
||||
finCount = 3 * fin.getFinCount();
|
||||
baseRotation = fin.getBaseRotation();
|
||||
cantAngle = 0;
|
||||
span = 2 * fin.getOuterRadius();
|
||||
finArea = span * fin.getLength();
|
||||
crossSection = FinSet.CrossSection.SQUARE;
|
||||
|
||||
calculateFinGeometry(fin);
|
||||
calculatePoly();
|
||||
interferenceFinCount = calculateInterferenceFinCount(fin);
|
||||
}
|
||||
|
||||
/*
|
||||
* Calculates the non-axial forces produced by the fins (normal and side forces,
|
||||
* pitch, yaw and roll moments, CP position, CNa).
|
||||
*/
|
||||
@Override
|
||||
public void calculateNonaxialForces(FlightConditions conditions, Transformation transform,
|
||||
AerodynamicForces forces) {
|
||||
|
||||
if (span < 0.001) {
|
||||
forces.setCm(0);
|
||||
forces.setCN(0);
|
||||
forces.setCNa(0);
|
||||
forces.setCP(Coordinate.NUL);
|
||||
forces.setCroll(0);
|
||||
forces.setCrollDamp(0);
|
||||
forces.setCrollForce(0);
|
||||
forces.setCside(0);
|
||||
forces.setCyaw(0);
|
||||
return;
|
||||
}
|
||||
|
||||
// Add warnings (radius/2 == diameter/4)
|
||||
if( (0 < bodyRadius) && (thickness > bodyRadius / 2)){
|
||||
warnings.add(Warning.THICK_FIN);
|
||||
}
|
||||
warnings.add(new Other("Tube fin support is experimental"));
|
||||
|
||||
//////// Calculate CNa. /////////
|
||||
|
||||
// One fin without interference (both sub- and supersonic):
|
||||
double cna1 = calculateFinCNa1(conditions);
|
||||
|
||||
// log.debug("Component cna1 = {}", cna1);
|
||||
|
||||
// Multiple fins with fin-fin interference
|
||||
double cna;
|
||||
double theta = conditions.getTheta();
|
||||
double angle = baseRotation + transform.getXrotation();
|
||||
|
||||
// Compute basic CNa without interference effects
|
||||
if (finCount == 1 || finCount == 2) {
|
||||
// Basic CNa from geometry
|
||||
double mul = 0;
|
||||
for (int i = 0; i < finCount; i++) {
|
||||
mul += MathUtil.pow2(Math.sin(theta - angle));
|
||||
angle += 2 * Math.PI / finCount;
|
||||
}
|
||||
cna = cna1 * mul;
|
||||
} else {
|
||||
// Basic CNa assuming full efficiency
|
||||
cna = cna1 * finCount / 2.0;
|
||||
}
|
||||
|
||||
// log.debug("Component cna = {}", cna);
|
||||
|
||||
// Take into account fin-fin interference effects
|
||||
switch (interferenceFinCount) {
|
||||
case 1:
|
||||
case 2:
|
||||
case 3:
|
||||
case 4:
|
||||
// No interference effect
|
||||
break;
|
||||
|
||||
case 5:
|
||||
cna *= 0.948;
|
||||
break;
|
||||
|
||||
case 6:
|
||||
cna *= 0.913;
|
||||
break;
|
||||
|
||||
case 7:
|
||||
cna *= 0.854;
|
||||
break;
|
||||
|
||||
case 8:
|
||||
cna *= 0.81;
|
||||
break;
|
||||
|
||||
default:
|
||||
// Assume 75% efficiency
|
||||
cna *= 0.75;
|
||||
break;
|
||||
}
|
||||
|
||||
|
||||
// Body-fin interference effect
|
||||
double r = bodyRadius;
|
||||
double tau = r / (span + r);
|
||||
if (Double.isNaN(tau) || Double.isInfinite(tau))
|
||||
tau = 0;
|
||||
cna *= 1 + tau; // Classical Barrowman
|
||||
// cna *= pow2(1 + tau); // Barrowman thesis (too optimistic??)
|
||||
// log.debug("Component cna = {}", cna);
|
||||
|
||||
// TODO: LOW: check for fin tip mach cone interference
|
||||
// (Barrowman thesis pdf-page 40)
|
||||
|
||||
// TODO: LOW: fin-fin mach cone effect, MIL-HDBK page 5-25
|
||||
|
||||
// Calculate CP position
|
||||
double x = macLead + calculateCPPos(conditions) * macLength;
|
||||
// log.debug("Component macLead = {}", macLead);
|
||||
// log.debug("Component macLength = {}", macLength);
|
||||
// log.debug("Component x = {}", x);
|
||||
|
||||
|
||||
// Calculate roll forces, reduce forcing above stall angle
|
||||
|
||||
// Without body-fin interference effect:
|
||||
// forces.CrollForce = fins * (macSpan+r) * cna1 * component.getCantAngle() /
|
||||
// conditions.getRefLength();
|
||||
// With body-fin interference effect:
|
||||
forces.setCrollForce(finCount * (macSpan + r) * cna1 * (1 + tau) * cantAngle / conditions.getRefLength());
|
||||
|
||||
if (conditions.getAOA() > STALL_ANGLE) {
|
||||
// System.out.println("Fin stalling in roll");
|
||||
forces.setCrollForce(forces.getCrollForce() * MathUtil.clamp(
|
||||
1 - (conditions.getAOA() - STALL_ANGLE) / (STALL_ANGLE / 2), 0, 1));
|
||||
}
|
||||
forces.setCrollDamp(calculateDampingMoment(conditions));
|
||||
forces.setCroll(forces.getCrollForce() - forces.getCrollDamp());
|
||||
|
||||
// System.out.printf(component.getName() + ": roll rate:%.3f force:%.3f damp:%.3f " +
|
||||
// "total:%.3f\n",
|
||||
// conditions.getRollRate(), forces.CrollForce, forces.CrollDamp, forces.Croll);
|
||||
|
||||
forces.setCNa(cna);
|
||||
forces.setCN(cna * MathUtil.min(conditions.getAOA(), STALL_ANGLE));
|
||||
forces.setCP(new Coordinate(x, 0, 0, cna));
|
||||
forces.setCm(forces.getCN() * x / conditions.getRefLength());
|
||||
|
||||
/*
|
||||
* TODO: HIGH: Compute actual side force and yaw moment.
|
||||
* This is not currently performed because it produces strange results for
|
||||
* stable rockets that have two fins in the front part of the fuselage,
|
||||
* where the rocket flies at an ever-increasing angle of attack. This may
|
||||
* be due to incorrect computation of pitch/yaw damping moments.
|
||||
*/
|
||||
// if (fins == 1 || fins == 2) {
|
||||
// forces.Cside = fins * cna1 * Math.cos(theta-angle) * Math.sin(theta-angle);
|
||||
// forces.Cyaw = fins * forces.Cside * x / conditions.getRefLength();
|
||||
// } else {
|
||||
// forces.Cside = 0;
|
||||
// forces.Cyaw = 0;
|
||||
// }
|
||||
forces.setCside(0);
|
||||
forces.setCyaw(0);
|
||||
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns the MAC length of the fin. This is required in the friction drag
|
||||
* computation.
|
||||
*
|
||||
* @return the MAC length of the fin.
|
||||
*/
|
||||
public double getMACLength() {
|
||||
return macLength;
|
||||
}
|
||||
|
||||
public double getMidchordPos() {
|
||||
return macLead + 0.5 * macLength;
|
||||
}
|
||||
|
||||
/**
|
||||
* Pre-calculates the fin geometry values.
|
||||
*/
|
||||
protected void calculateFinGeometry(TubeFinSet component) {
|
||||
|
||||
ar = 2 * pow2(span) / finArea;
|
||||
|
||||
Coordinate[] points = {
|
||||
Coordinate.NUL,
|
||||
new Coordinate(0, span),
|
||||
new Coordinate(component.getLength(), span),
|
||||
new Coordinate(component.getLength(), 0)
|
||||
};
|
||||
|
||||
|
||||
// Calculate the chord lead and trail positions and length
|
||||
|
||||
Arrays.fill(chordLead, Double.POSITIVE_INFINITY);
|
||||
Arrays.fill(chordTrail, Double.NEGATIVE_INFINITY);
|
||||
Arrays.fill(chordLength, 0);
|
||||
|
||||
for (int point = 1; point < points.length; point++) {
|
||||
double x1 = points[point - 1].x;
|
||||
double y1 = points[point - 1].y;
|
||||
double x2 = points[point].x;
|
||||
double y2 = points[point].y;
|
||||
|
||||
// Don't use the default EPSILON since it is too small
|
||||
// and causes too much numerical instability in the computation of x below
|
||||
if (MathUtil.equals(y1, y2, 0.001))
|
||||
continue;
|
||||
|
||||
int i1 = (int) (y1 * 1.0001 / span * (DIVISIONS - 1));
|
||||
int i2 = (int) (y2 * 1.0001 / span * (DIVISIONS - 1));
|
||||
i1 = MathUtil.clamp(i1, 0, DIVISIONS - 1);
|
||||
i2 = MathUtil.clamp(i2, 0, DIVISIONS - 1);
|
||||
if (i1 > i2) {
|
||||
int tmp = i2;
|
||||
i2 = i1;
|
||||
i1 = tmp;
|
||||
}
|
||||
|
||||
for (int i = i1; i <= i2; i++) {
|
||||
// Intersection point (x,y)
|
||||
double y = i * span / (DIVISIONS - 1);
|
||||
double x = (y - y2) / (y1 - y2) * x1 + (y1 - y) / (y1 - y2) * x2;
|
||||
if (x < chordLead[i])
|
||||
chordLead[i] = x;
|
||||
if (x > chordTrail[i])
|
||||
chordTrail[i] = x;
|
||||
|
||||
// TODO: LOW: If fin point exactly on chord line, might be counted twice:
|
||||
if (y1 < y2) {
|
||||
chordLength[i] -= x;
|
||||
} else {
|
||||
chordLength[i] += x;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// Check and correct any inconsistencies
|
||||
for (int i = 0; i < DIVISIONS; i++) {
|
||||
if (Double.isInfinite(chordLead[i]) || Double.isInfinite(chordTrail[i]) ||
|
||||
Double.isNaN(chordLead[i]) || Double.isNaN(chordTrail[i])) {
|
||||
chordLead[i] = 0;
|
||||
chordTrail[i] = 0;
|
||||
}
|
||||
if (chordLength[i] < 0 || Double.isNaN(chordLength[i])) {
|
||||
chordLength[i] = 0;
|
||||
}
|
||||
if (chordLength[i] > chordTrail[i] - chordLead[i]) {
|
||||
chordLength[i] = chordTrail[i] - chordLead[i];
|
||||
}
|
||||
}
|
||||
|
||||
/* Calculate fin properties:
|
||||
*
|
||||
* macLength // MAC length
|
||||
* macLead // MAC leading edge position
|
||||
* macSpan // MAC spanwise position
|
||||
* ar // Fin aspect ratio (already set)
|
||||
* span // Fin span (already set)
|
||||
*/
|
||||
macLength = 0;
|
||||
macLead = 0;
|
||||
macSpan = 0;
|
||||
cosGamma = 0;
|
||||
cosGammaLead = 0;
|
||||
rollSum = 0;
|
||||
double area = 0;
|
||||
double radius = component.getBodyRadius();
|
||||
|
||||
final double dy = span / (DIVISIONS - 1);
|
||||
for (int i = 0; i < DIVISIONS; i++) {
|
||||
double length = chordTrail[i] - chordLead[i];
|
||||
double y = i * dy;
|
||||
|
||||
macLength += length * length;
|
||||
log.debug("macLength = {}, length = {}, i = {}", macLength, length, i);
|
||||
macSpan += y * length;
|
||||
macLead += chordLead[i] * length;
|
||||
area += length;
|
||||
rollSum += chordLength[i] * pow2(radius + y);
|
||||
|
||||
if (i > 0) {
|
||||
double dx = (chordTrail[i] + chordLead[i]) / 2 - (chordTrail[i - 1] + chordLead[i - 1]) / 2;
|
||||
cosGamma += dy / MathUtil.hypot(dx, dy);
|
||||
|
||||
dx = chordLead[i] - chordLead[i - 1];
|
||||
cosGammaLead += dy / MathUtil.hypot(dx, dy);
|
||||
}
|
||||
}
|
||||
|
||||
macLength *= dy;
|
||||
log.debug("macLength = {}", macLength);
|
||||
macSpan *= dy;
|
||||
macLead *= dy;
|
||||
area *= dy;
|
||||
rollSum *= dy;
|
||||
|
||||
macLength /= area;
|
||||
macSpan /= area;
|
||||
macLead /= area;
|
||||
cosGamma /= (DIVISIONS - 1);
|
||||
cosGammaLead /= (DIVISIONS - 1);
|
||||
}
|
||||
|
||||
/////////////// CNa1 calculation ////////////////
|
||||
|
||||
private static final double CNA_SUBSONIC = 0.9;
|
||||
private static final double CNA_SUPERSONIC = 1.5;
|
||||
private static final double CNA_SUPERSONIC_B = pow(pow2(CNA_SUPERSONIC) - 1, 1.5);
|
||||
private static final double GAMMA = 1.4;
|
||||
private static final LinearInterpolator K1, K2, K3;
|
||||
private static final PolyInterpolator cnaInterpolator = new PolyInterpolator(
|
||||
new double[] { CNA_SUBSONIC, CNA_SUPERSONIC },
|
||||
new double[] { CNA_SUBSONIC, CNA_SUPERSONIC },
|
||||
new double[] { CNA_SUBSONIC }
|
||||
);
|
||||
/* Pre-calculate the values for K1, K2 and K3 */
|
||||
static {
|
||||
// Up to Mach 5
|
||||
int n = (int) ((5.0 - CNA_SUPERSONIC) * 10);
|
||||
double[] x = new double[n];
|
||||
double[] k1 = new double[n];
|
||||
double[] k2 = new double[n];
|
||||
double[] k3 = new double[n];
|
||||
for (int i = 0; i < n; i++) {
|
||||
double M = CNA_SUPERSONIC + i * 0.1;
|
||||
double beta = MathUtil.safeSqrt(M * M - 1);
|
||||
x[i] = M;
|
||||
k1[i] = 2.0 / beta;
|
||||
k2[i] = ((GAMMA + 1) * pow(M, 4) - 4 * pow2(beta)) / (4 * pow(beta, 4));
|
||||
k3[i] = ((GAMMA + 1) * pow(M, 8) + (2 * pow2(GAMMA) - 7 * GAMMA - 5) * pow(M, 6) +
|
||||
10 * (GAMMA + 1) * pow(M, 4) + 8) / (6 * pow(beta, 7));
|
||||
}
|
||||
K1 = new LinearInterpolator(x, k1);
|
||||
K2 = new LinearInterpolator(x, k2);
|
||||
K3 = new LinearInterpolator(x, k3);
|
||||
|
||||
// System.out.println("K1[m="+CNA_SUPERSONIC+"] = "+k1[0]);
|
||||
// System.out.println("K2[m="+CNA_SUPERSONIC+"] = "+k2[0]);
|
||||
// System.out.println("K3[m="+CNA_SUPERSONIC+"] = "+k3[0]);
|
||||
}
|
||||
|
||||
protected double calculateFinCNa1(FlightConditions conditions) {
|
||||
double mach = conditions.getMach();
|
||||
double ref = conditions.getRefArea();
|
||||
double alpha = MathUtil.min(conditions.getAOA(),
|
||||
Math.PI - conditions.getAOA(), STALL_ANGLE);
|
||||
|
||||
// Subsonic case
|
||||
if (mach <= CNA_SUBSONIC) {
|
||||
return 2 * Math.PI * pow2(span) / (1 + MathUtil.safeSqrt(1 + (1 - pow2(mach)) *
|
||||
pow2(pow2(span) / (finArea * cosGamma)))) / ref;
|
||||
}
|
||||
|
||||
// Supersonic case
|
||||
if (mach >= CNA_SUPERSONIC) {
|
||||
return finArea * (K1.getValue(mach) + K2.getValue(mach) * alpha +
|
||||
K3.getValue(mach) * pow2(alpha)) / ref;
|
||||
}
|
||||
|
||||
// Transonic case, interpolate
|
||||
double subV, superV;
|
||||
double subD, superD;
|
||||
|
||||
double sq = MathUtil.safeSqrt(1 + (1 - pow2(CNA_SUBSONIC)) * pow2(span * span / (finArea * cosGamma)));
|
||||
subV = 2 * Math.PI * pow2(span) / ref / (1 + sq);
|
||||
subD = 2 * mach * Math.PI * pow(span, 6) / (pow2(finArea * cosGamma) * ref *
|
||||
sq * pow2(1 + sq));
|
||||
|
||||
superV = finArea * (K1.getValue(CNA_SUPERSONIC) + K2.getValue(CNA_SUPERSONIC) * alpha +
|
||||
K3.getValue(CNA_SUPERSONIC) * pow2(alpha)) / ref;
|
||||
superD = -finArea / ref * 2 * CNA_SUPERSONIC / CNA_SUPERSONIC_B;
|
||||
|
||||
// System.out.println("subV="+subV+" superV="+superV+" subD="+subD+" superD="+superD);
|
||||
|
||||
return cnaInterpolator.interpolate(mach, subV, superV, subD, superD, 0);
|
||||
}
|
||||
|
||||
private double calculateDampingMoment(FlightConditions conditions) {
|
||||
double rollRate = conditions.getRollRate();
|
||||
|
||||
if (Math.abs(rollRate) < 0.1)
|
||||
return 0;
|
||||
|
||||
double mach = conditions.getMach();
|
||||
double absRate = Math.abs(rollRate);
|
||||
|
||||
/*
|
||||
* At low speeds and relatively large roll rates (i.e. near apogee) the
|
||||
* fin tips rotate well above stall angle. In this case sum the chords
|
||||
* separately.
|
||||
*/
|
||||
if (absRate * (bodyRadius + span) / conditions.getVelocity() > 15 * Math.PI / 180) {
|
||||
double sum = 0;
|
||||
for (int i = 0; i < DIVISIONS; i++) {
|
||||
double dist = bodyRadius + span * i / DIVISIONS;
|
||||
double aoa = Math.min(absRate * dist / conditions.getVelocity(), 15 * Math.PI / 180);
|
||||
sum += chordLength[i] * dist * aoa;
|
||||
}
|
||||
sum = sum * (span / DIVISIONS) * 2 * Math.PI / conditions.getBeta() /
|
||||
(conditions.getRefArea() * conditions.getRefLength());
|
||||
|
||||
// System.out.println("SPECIAL: " +
|
||||
// (MathUtil.sign(rollRate) *component.getFinCount() * sum));
|
||||
return MathUtil.sign(rollRate) * finCount * sum;
|
||||
}
|
||||
|
||||
if (mach <= CNA_SUBSONIC) {
|
||||
// System.out.println("BASIC: "+
|
||||
// (component.getFinCount() * 2*Math.PI * rollRate * rollSum /
|
||||
// (conditions.getRefArea() * conditions.getRefLength() *
|
||||
// conditions.getVelocity() * conditions.getBeta())));
|
||||
|
||||
return finCount * 2 * Math.PI * rollRate * rollSum /
|
||||
(conditions.getRefArea() * conditions.getRefLength() *
|
||||
conditions.getVelocity() * conditions.getBeta());
|
||||
}
|
||||
if (mach >= CNA_SUPERSONIC) {
|
||||
|
||||
double vel = conditions.getVelocity();
|
||||
double k1 = K1.getValue(mach);
|
||||
double k2 = K2.getValue(mach);
|
||||
double k3 = K3.getValue(mach);
|
||||
|
||||
double sum = 0;
|
||||
|
||||
for (int i = 0; i < DIVISIONS; i++) {
|
||||
double y = i * span / (DIVISIONS - 1);
|
||||
double angle = rollRate * (bodyRadius + y) / vel;
|
||||
|
||||
sum += (k1 * angle + k2 * angle * angle + k3 * angle * angle * angle)
|
||||
* chordLength[i] * (bodyRadius + y);
|
||||
}
|
||||
|
||||
return finCount * sum * span / (DIVISIONS - 1) /
|
||||
(conditions.getRefArea() * conditions.getRefLength());
|
||||
}
|
||||
|
||||
// Transonic, do linear interpolation
|
||||
|
||||
FlightConditions cond = conditions.clone();
|
||||
cond.setMach(CNA_SUBSONIC - 0.01);
|
||||
double subsonic = calculateDampingMoment(cond);
|
||||
cond.setMach(CNA_SUPERSONIC + 0.01);
|
||||
double supersonic = calculateDampingMoment(cond);
|
||||
|
||||
return subsonic * (CNA_SUPERSONIC - mach) / (CNA_SUPERSONIC - CNA_SUBSONIC) +
|
||||
supersonic * (mach - CNA_SUBSONIC) / (CNA_SUPERSONIC - CNA_SUBSONIC);
|
||||
}
|
||||
|
||||
/**
|
||||
* Return the relative position of the CP along the mean aerodynamic chord.
|
||||
* Below mach 0.5 it is at the quarter chord, above mach 2 calculated using an
|
||||
* empirical formula, between these two using an interpolation polynomial.
|
||||
*
|
||||
* @param cond Mach speed used
|
||||
* @return CP position along the MAC
|
||||
*/
|
||||
private double calculateCPPos(FlightConditions cond) {
|
||||
double m = cond.getMach();
|
||||
// log.debug("m = {} ", m);
|
||||
if (m <= 0.5) {
|
||||
// At subsonic speeds CP at quarter chord
|
||||
return 0.25;
|
||||
}
|
||||
if (m >= 2) {
|
||||
// At supersonic speeds use empirical formula
|
||||
double beta = cond.getBeta();
|
||||
return (ar * beta - 0.67) / (2 * ar * beta - 1);
|
||||
}
|
||||
|
||||
// In between use interpolation polynomial
|
||||
double x = 1.0;
|
||||
double val = 0;
|
||||
|
||||
for (int i = 0; i < poly.length; i++) {
|
||||
val += poly[i] * x;
|
||||
x *= m;
|
||||
}
|
||||
// log.debug("val = {}", val);
|
||||
return val;
|
||||
}
|
||||
|
||||
/**
|
||||
* Calculate CP position interpolation polynomial coefficients from the
|
||||
* fin geometry. This is a fifth order polynomial that satisfies
|
||||
*
|
||||
* p(0.5)=0.25
|
||||
* p'(0.5)=0
|
||||
* p(2) = f(2)
|
||||
* p'(2) = f'(2)
|
||||
* p''(2) = 0
|
||||
* p'''(2) = 0
|
||||
*
|
||||
* where f(M) = (ar*sqrt(M^2-1) - 0.67) / (2*ar*sqrt(M^2-1) - 1).
|
||||
*
|
||||
* The values were calculated analytically in Mathematica. The coefficients
|
||||
* are used as poly[0] + poly[1]*x + poly[2]*x^2 + ...
|
||||
*/
|
||||
private void calculatePoly() {
|
||||
double denom = pow2(1 - 3.4641 * ar); // common denominator
|
||||
|
||||
poly[5] = (-1.58025 * (-0.728769 + ar) * (-0.192105 + ar)) / denom;
|
||||
poly[4] = (12.8395 * (-0.725688 + ar) * (-0.19292 + ar)) / denom;
|
||||
poly[3] = (-39.5062 * (-0.72074 + ar) * (-0.194245 + ar)) / denom;
|
||||
poly[2] = (55.3086 * (-0.711482 + ar) * (-0.196772 + ar)) / denom;
|
||||
poly[1] = (-31.6049 * (-0.705375 + ar) * (-0.198476 + ar)) / denom;
|
||||
poly[0] = (9.16049 * (-0.588838 + ar) * (-0.20624 + ar)) / denom;
|
||||
}
|
||||
|
||||
|
||||
// @SuppressWarnings("null")
|
||||
// public static void main(String arg[]) {
|
||||
// Rocket rocket = TestRocket.makeRocket();
|
||||
// FinSet finset = null;
|
||||
//
|
||||
// Iterator<RocketComponent> iter = rocket.deepIterator();
|
||||
// while (iter.hasNext()) {
|
||||
// RocketComponent c = iter.next();
|
||||
// if (c instanceof FinSet) {
|
||||
// finset = (FinSet)c;
|
||||
// break;
|
||||
// }
|
||||
// }
|
||||
//
|
||||
// ((TrapezoidFinSet)finset).setHeight(0.10);
|
||||
// ((TrapezoidFinSet)finset).setRootChord(0.10);
|
||||
// ((TrapezoidFinSet)finset).setTipChord(0.10);
|
||||
// ((TrapezoidFinSet)finset).setSweep(0.0);
|
||||
//
|
||||
//
|
||||
// FinSetCalc calc = new FinSetCalc(finset);
|
||||
//
|
||||
// calc.calculateFinGeometry();
|
||||
// FlightConditions cond = new FlightConditions(new Configuration(rocket));
|
||||
// for (double m=0; m < 3; m+=0.05) {
|
||||
// cond.setMach(m);
|
||||
// cond.setAOA(0.0*Math.PI/180);
|
||||
// double cna = calc.calculateFinCNa1(cond);
|
||||
// System.out.printf("%5.2f "+cna+"\n", m);
|
||||
// }
|
||||
//
|
||||
// }
|
||||
|
||||
@Override
|
||||
public double calculateFrictionCD(FlightConditions conditions, double componentCf, WarningSet warnings) {
|
||||
if (tubeFinSet.getTubeSeparation() > MathUtil.EPSILON) {
|
||||
warnings.add(Warning.TUBE_SEPARATION);
|
||||
} else if (tubeFinSet.getTubeSeparation() < -MathUtil.EPSILON) {
|
||||
warnings.add(Warning.TUBE_OVERLAP);
|
||||
}
|
||||
|
||||
// Area of inner surface of tubes.
|
||||
final double innerArea = tubeFinSet.getFinCount() * tubeFinSet.getLength() * 2.0 * Math.PI * tubeFinSet.getInnerRadius();
|
||||
|
||||
// Area of the outer surface of tubes. Since roughly half
|
||||
// of the area is "masked" by the interstices between the tubes and the
|
||||
// body tube, only consider half the area
|
||||
final double outerArea = tubeFinSet.getFinCount() * tubeFinSet.getLength() * Math.PI * tubeFinSet.getOuterRadius();
|
||||
|
||||
// Area of the portion of the body tube masked by the tube fins
|
||||
final BodyTube parent = (BodyTube) tubeFinSet.getParent();
|
||||
final double maskedArea = tubeFinSet.getLength() * 2.0 * Math.PI * parent.getOuterRadius();
|
||||
|
||||
final double frictionCD = componentCf * (innerArea + outerArea - maskedArea);
|
||||
log.debug("frictionCD " + frictionCD);
|
||||
return frictionCD;
|
||||
}
|
||||
|
||||
@Override
|
||||
public double calculatePressureCD(FlightConditions conditions,
|
||||
double stagnationCD, double baseCD, WarningSet warnings) {
|
||||
|
||||
double mach = conditions.getMach();
|
||||
double cd = 0;
|
||||
|
||||
// Effective frontal area of tubes based on actual area and length of tubes
|
||||
|
||||
// Area of interstices. Assume they're long enough compared to other dimensions
|
||||
// they can be modeled as blunt
|
||||
|
||||
// Pressure fore-drag.
|
||||
if (crossSection == FinSet.CrossSection.AIRFOIL ||
|
||||
crossSection == FinSet.CrossSection.ROUNDED) {
|
||||
|
||||
// Round leading edge
|
||||
if (mach < 0.9) {
|
||||
cd = Math.pow(1 - pow2(mach), -0.417) - 1;
|
||||
} else if (mach < 1) {
|
||||
cd = 1 - 1.785 * (mach - 0.9);
|
||||
} else {
|
||||
cd = 1.214 - 0.502 / pow2(mach) + 0.1095 / pow2(pow2(mach));
|
||||
}
|
||||
|
||||
} else if (crossSection == FinSet.CrossSection.SQUARE) {
|
||||
cd = stagnationCD;
|
||||
} else {
|
||||
throw new UnsupportedOperationException("Unsupported fin profile: " + crossSection);
|
||||
}
|
||||
|
||||
// Slanted leading edge
|
||||
cd *= pow2(cosGammaLead);
|
||||
|
||||
// Trailing edge drag
|
||||
if (crossSection == FinSet.CrossSection.SQUARE) {
|
||||
cd += baseCD;
|
||||
} else if (crossSection == FinSet.CrossSection.ROUNDED) {
|
||||
cd += baseCD / 2;
|
||||
}
|
||||
// Airfoil assumed to have zero base drag
|
||||
|
||||
// Scale to correct reference area
|
||||
cd *= finCount * span * thickness / conditions.getRefArea();
|
||||
|
||||
return cd;
|
||||
}
|
||||
|
||||
private static int calculateInterferenceFinCount(TubeFinSet component) {
|
||||
RocketComponent parent = component.getParent();
|
||||
if (parent == null) {
|
||||
throw new IllegalStateException("fin set without parent component");
|
||||
}
|
||||
|
||||
return 3 * component.getFinCount();
|
||||
}
|
||||
}
|
||||
Loading…
x
Reference in New Issue
Block a user