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commit the work-in-progress drag calculations, including creating TubeCalc for calculations common to LaunchLugs and TubeFinSets

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This commit is contained in:
JoePfeiffer 2022-04-20 15:42:19 -06:00
parent 2c4ebabaa1
commit 4477d9226e
5 changed files with 115 additions and 97 deletions
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3
core/resources/l10n/messages.properties
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@ -1756,6 +1756,9 @@ Warning.TUMBLE_UNDER_THRUST = Stage began to tumble under thrust.
Warning.EVENT_AFTER_LANDING = Flight Event occurred after landing:
Warning.ZERO_LENGTH_BODY = Zero length bodies may not result in accurate simulations.
Warning.ZERO_RADIUS_BODY = Zero length bodies may not result in accurate simulations.
Warning.TUBE_STABILITY = Tube fin stability calculations may not be accurate.
Warning.TUBE_SEPARATION = Space between tube fins may not result in accurate simulations.
Warning.TUBE_OVERLAP = Overlapping tube fins may not result in accurate simulations.
! Scale dialog
ScaleDialog.lbl.scaleRocket = Entire rocket

3
core/src/net/sf/openrocket/aerodynamics/Warning.java
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@ -392,4 +392,7 @@ public abstract class Warning {
public static final Warning ZERO_LENGTH_BODY = new Other(trans.get("Warning.ZERO_LENGTH_BODY"));
public static final Warning ZERO_RADIUS_BODY = new Other(trans.get("Warning.ZERO_RADIUS_BODY"));
public static final Warning TUBE_STABILITY = new Other(trans.get("Warning.TUBE_STABILITY"));
public static final Warning TUBE_SEPARATION = new Other(trans.get("Warning.TUBE_SEPARATION"));
public static final Warning TUBE_OVERLAP = new Other(trans.get("Warning.TUBE_OVERLAP"));
}

2
core/src/net/sf/openrocket/aerodynamics/barrowman/LaunchLugCalc.java
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@ -8,7 +8,7 @@ import net.sf.openrocket.rocketcomponent.RocketComponent;
import net.sf.openrocket.util.MathUtil;
import net.sf.openrocket.util.Transformation;
public class LaunchLugCalc extends RocketComponentCalc {
public class LaunchLugCalc extends TubeCalc {
private final double CDmul;
private final double refArea;

27
core/src/net/sf/openrocket/aerodynamics/barrowman/TubeCalc.java Normal file
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@ -0,0 +1,27 @@
package net.sf.openrocket.aerodynamics.barrowman;
import net.sf.openrocket.aerodynamics.AerodynamicForces;
import net.sf.openrocket.aerodynamics.FlightConditions;
import net.sf.openrocket.aerodynamics.WarningSet;
import net.sf.openrocket.rocketcomponent.LaunchLug;
import net.sf.openrocket.rocketcomponent.RocketComponent;
import net.sf.openrocket.util.MathUtil;
import net.sf.openrocket.util.Transformation;
public abstract class TubeCalc extends RocketComponentCalc {
private final double CDmul;
protected final double refArea;
public TubeCalc(RocketComponent component) {
super(component);
LaunchLug lug = (LaunchLug)component;
double ld = lug.getLength() / (2*lug.getOuterRadius());
CDmul = Math.max(1.3 - ld, 1);
refArea = Math.PI * MathUtil.pow2(lug.getOuterRadius()) -
Math.PI * MathUtil.pow2(lug.getInnerRadius()) * Math.max(1 - ld, 0);
}
}

161
core/src/net/sf/openrocket/aerodynamics/barrowman/TubeFinSetCalc.java
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@ -10,6 +10,7 @@ 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;
@ -33,9 +34,9 @@ import org.slf4j.LoggerFactory;
* @author kruland
*
*/
public class TubeFinSetCalc extends RocketComponentCalc {
public class TubeFinSetCalc extends TubeCalc {
private final static Logger logger = LoggerFactory.getLogger(FinSetCalc.class);
private final static Logger log = LoggerFactory.getLogger(FinSetCalc.class);
private static final double STALL_ANGLE = (20 * Math.PI / 180);
@ -57,8 +58,13 @@ public class TubeFinSetCalc extends RocketComponentCalc {
protected double[] chordTrail = new double[DIVISIONS];
protected double[] chordLength = new double[DIVISIONS];
protected final WarningSet geometryWarnings = new WarningSet();
private final double[] poly = new double[6];
private final double wettedArea;
private final double frontalArea;
private final double thickness;
private final double bodyRadius;
private final int finCount;
@ -73,9 +79,52 @@ public class TubeFinSetCalc extends RocketComponentCalc {
throw new IllegalArgumentException("Illegal component type " + component);
}
TubeFinSet fin = (TubeFinSet) component;
final TubeFinSet tubes = (TubeFinSet) component;
final TubeFinSet fin = tubes; // keep this around while we're still leveraging FinSet
geometryWarnings.add(Warning.TUBE_STABILITY);
if (tubes.getTubeSeparation() > MathUtil.EPSILON) {
geometryWarnings.add(Warning.TUBE_SEPARATION);
} else if (tubes.getTubeSeparation() < -MathUtil.EPSILON) {
geometryWarnings.add(Warning.TUBE_OVERLAP);
}
// precompute geometry
bodyRadius = tubes.getBodyRadius();
// wetted area for friction drag calculation
// Area of inner surface of tubes.
final double innerArea = tubes.getFinCount() * tubes.getLength() * 2.0 * Math.PI * tubes.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 = tubes.getFinCount() * tubes.getLength() * Math.PI * tubes.getOuterRadius();
// Area of the portion of the body tube masked by the tube fins
final BodyTube parent = (BodyTube) tubes.getParent();
final double maskedArea = tubes.getLength() * 2.0 * Math.PI * parent.getOuterRadius();
wettedArea = innerArea + outerArea - maskedArea;
log.debug("wetted area of tube fins " + wettedArea);
// effective frontal area for pressure drag calculation
// model interstices between tube fins and body tube as closed blunt area
// area of disk passing through tube fin centers
final double tubeDiskArea = Math.PI * MathUtil.pow2(bodyRadius + tubes.getOuterRadius());
// half of combined area of tube fin interiors.
final double tubeInnerArea = tubes.getFinCount() * Math.PI * MathUtil.pow2(tubes.getInnerRadius()) / 2.0;
// body tube area
final double bodyTubeArea = Math.PI * MathUtil.pow2(bodyRadius);
// refArea is effective frontal area of a tube, from LaunchLugCalc
frontalArea = tubes.getFinCount() * refArea + tubeDiskArea - tubeInnerArea - bodyTubeArea;
log.debug("effective frontal area " + frontalArea);
thickness = fin.getThickness();
bodyRadius = fin.getBodyRadius();
finCount = 3 * fin.getFinCount();
baseRotation = fin.getBaseRotation();
cantAngle = 0;
@ -113,14 +162,13 @@ public class TubeFinSetCalc extends RocketComponentCalc {
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);
// logger.debug("Component cna1 = {}", cna1);
// log.debug("Component cna1 = {}", cna1);
// Multiple fins with fin-fin interference
double cna;
@ -141,7 +189,7 @@ public class TubeFinSetCalc extends RocketComponentCalc {
cna = cna1 * finCount / 2.0;
}
// logger.debug("Component cna = {}", cna);
// log.debug("Component cna = {}", cna);
// Take into account fin-fin interference effects
switch (interferenceFinCount) {
@ -182,7 +230,7 @@ public class TubeFinSetCalc extends RocketComponentCalc {
tau = 0;
cna *= 1 + tau; // Classical Barrowman
// cna *= pow2(1 + tau); // Barrowman thesis (too optimistic??)
// logger.debug("Component cna = {}", cna);
// log.debug("Component cna = {}", cna);
// TODO: LOW: check for fin tip mach cone interference
// (Barrowman thesis pdf-page 40)
@ -191,9 +239,9 @@ public class TubeFinSetCalc extends RocketComponentCalc {
// Calculate CP position
double x = macLead + calculateCPPos(conditions) * macLength;
// logger.debug("Component macLead = {}", macLead);
// logger.debug("Component macLength = {}", macLength);
// logger.debug("Component x = {}", x);
// log.debug("Component macLead = {}", macLead);
// log.debug("Component macLength = {}", macLength);
// log.debug("Component x = {}", x);
// Calculate roll forces, reduce forcing above stall angle
@ -352,7 +400,7 @@ public class TubeFinSetCalc extends RocketComponentCalc {
double y = i * dy;
macLength += length * length;
logger.debug("macLength = {}, length = {}, i = {}", macLength, length, i);
log.debug("macLength = {}, length = {}, i = {}", macLength, length, i);
macSpan += y * length;
macLead += chordLead[i] * length;
area += length;
@ -368,7 +416,7 @@ public class TubeFinSetCalc extends RocketComponentCalc {
}
macLength *= dy;
logger.debug("macLength = {}", macLength);
log.debug("macLength = {}", macLength);
macSpan *= dy;
macLead *= dy;
area *= dy;
@ -537,7 +585,7 @@ public class TubeFinSetCalc extends RocketComponentCalc {
*/
private double calculateCPPos(FlightConditions cond) {
double m = cond.getMach();
// logger.debug("m = {} ", m);
// log.debug("m = {} ", m);
if (m <= 0.5) {
// At subsonic speeds CP at quarter chord
return 0.25;
@ -556,7 +604,7 @@ public class TubeFinSetCalc extends RocketComponentCalc {
val += poly[i] * x;
x *= m;
}
// logger.debug("val = {}", val);
// log.debug("val = {}", val);
return val;
}
@ -587,79 +635,23 @@ public class TubeFinSetCalc extends RocketComponentCalc {
poly[0] = (9.16049 * (-0.588838 + ar) * (-0.20624 + ar)) / denom;
}
@Override
public double calculateFrictionCD(FlightConditions conditions, double componentCf, WarningSet warnings) {
warnings.addAll(geometryWarnings);
// @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);
// }
//
// }
final double frictionCD = componentCf * wettedArea / conditions.getRefArea();
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;
warnings.addAll(geometryWarnings);
// 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();
final double cd = (stagnationCD + baseCD) * frontalArea / conditions.getRefArea();
log.debug("pressure CD " + cd);
return cd;
}
@ -672,11 +664,4 @@ public class TubeFinSetCalc extends RocketComponentCalc {
return 3 * component.getFinCount();
}
@Override
public double calculateFrictionCD(FlightConditions conditions, double componentCf, WarningSet warnings) {
// launch lug doesn't add enough area to worry about
return 0;
}
}