Merge pull request #1413 from JoePfeiffer/fix-1258
Update tube fin stabililty calculations
This commit is contained in:
Joe Pfeiffer
GitHub
commit
ca9241f562
@ -1789,7 +1789,6 @@ Warning.TUMBLE_UNDER_THRUST = Stage began to tumble under thrust.
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Warning.EVENT_AFTER_LANDING = Flight Event occurred after landing:
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Warning.ZERO_LENGTH_BODY = Zero length bodies may not result in accurate simulations.
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Warning.ZERO_RADIUS_BODY = Zero length bodies may not result in accurate simulations.
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Warning.TUBE_STABILITY = Tube fin stability calculations may not be accurate.
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Warning.TUBE_SEPARATION = Space between tube fins may not result in accurate simulations.
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Warning.TUBE_OVERLAP = Overlapping tube fins may not result in accurate simulations.
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@ -392,7 +392,6 @@ public abstract class Warning {
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public static final Warning ZERO_LENGTH_BODY = new Other(trans.get("Warning.ZERO_LENGTH_BODY"));
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public static final Warning ZERO_RADIUS_BODY = new Other(trans.get("Warning.ZERO_RADIUS_BODY"));
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public static final Warning TUBE_STABILITY = new Other(trans.get("Warning.TUBE_STABILITY"));
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public static final Warning TUBE_SEPARATION = new Other(trans.get("Warning.TUBE_SEPARATION"));
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public static final Warning TUBE_OVERLAP = new Other(trans.get("Warning.TUBE_OVERLAP"));
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}
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@ -25,52 +25,32 @@ import org.slf4j.LoggerFactory;
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/**
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* Preliminary computation of tube fin aerodynamics.
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*
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* Uses a complete clone of FinSetCalc modelling each tube fin as 3 individual fins. It does not correctly account for
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* fin & tube fin interference.
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*
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* @author kruland
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*
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*/
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public class TubeFinSetCalc extends TubeCalc {
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private final static Logger log = LoggerFactory.getLogger(TubeFinSetCalc.class);
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final double intersticeArea;
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private static final double STALL_ANGLE = (20 * Math.PI / 180);
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private final double[] poly = new double[6];
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/** Number of divisions in the fin chords. */
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protected static final int DIVISIONS = 48;
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// parameters straight from configuration; we'll be grabbing them once
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// so code is a bit shorter elsewhere
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private final double bodyRadius;
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private final double chord;
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private final double innerRadius;
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private final double outerRadius;
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private final int tubeCount;
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private final double baseRotation;
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// at present tubes are only allowed a cant angle of 0
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private final double cantAngle;
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protected double macLength = Double.NaN; // MAC length
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protected double macLead = Double.NaN; // MAC leading edge position
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protected double macSpan = Double.NaN; // MAC spanwise position
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protected double finArea = Double.NaN; // Fin area
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protected double ar = Double.NaN; // Fin aspect ratio
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protected double span = Double.NaN; // Fin span
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protected double cosGamma = Double.NaN; // Cosine of midchord sweep angle
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protected double cosGammaLead = Double.NaN; // Cosine of leading edge sweep angle
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protected double rollSum = Double.NaN; // Roll damping sum term
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protected double[] chordLead = new double[DIVISIONS];
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protected double[] chordTrail = new double[DIVISIONS];
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protected double[] chordLength = new double[DIVISIONS];
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// values we can precompute once
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private final double ar;
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private final double intersticeArea;
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private final double wettedArea;
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private final double cnaconst;
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protected final WarningSet geometryWarnings = new WarningSet();
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private final double[] poly = new double[6];
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private final double wettedArea;
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private final double thickness;
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private final double bodyRadius;
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private final int finCount;
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private final double baseRotation;
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private final double cantAngle;
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protected final int interferenceFinCount;
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private final FinSet.CrossSection crossSection;
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public TubeFinSetCalc(RocketComponent component) {
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super(component);
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@ -79,62 +59,67 @@ public class TubeFinSetCalc extends TubeCalc {
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}
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final TubeFinSet tubes = (TubeFinSet) component;
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final TubeFinSet fin = tubes; // keep this around while we're still leveraging FinSet
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geometryWarnings.add(Warning.TUBE_STABILITY);
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if (tubes.getTubeSeparation() > MathUtil.EPSILON) {
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geometryWarnings.add(Warning.TUBE_SEPARATION);
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} else if (tubes.getTubeSeparation() < -MathUtil.EPSILON) {
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geometryWarnings.add(Warning.TUBE_OVERLAP);
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}
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bodyRadius = tubes.getBodyRadius();
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chord = tubes.getLength();
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innerRadius = tubes.getInnerRadius();
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outerRadius = tubes.getOuterRadius();
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tubeCount = tubes.getFinCount();
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baseRotation = tubes.getBaseRotation();
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// at present, tube cant angle can only be 0
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cantAngle = 0;
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// cantAngle = tubes.getCantAngle();
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// precompute geometry. This will be the geometry of a single tube, since BarrowmanCalculator
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// iterates across them. Doesn't consider interference between them; that should only be relevant for
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// fins that are either separated or overlapping.
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bodyRadius = tubes.getBodyRadius();
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// 1. wetted area for friction drag calculation. We don't consider the inner surface of the tube;
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// aspect ratio.
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ar = 2 * innerRadius / chord;
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// wetted area for friction drag calculation. We don't consider the inner surface of the tube;
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// that affects the pressure drop through the tube and so (indirecctly) affects the pressure drag.
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// Area of the outer surface of tubes. Since roughly half
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// of the area is "masked" by the interstices between the tubes and the
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// body tube, only consider the other half of the area
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final double outerArea = tubes.getLength() * Math.PI * tubes.getOuterRadius();
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// body tube, only consider the other half of the area (so only multiplying by pi instead of 2*pi)
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final double outerArea = chord * Math.PI * outerRadius;
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// Surface area of the portion of the body tube masked by the tube fins, per tube
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final BodyTube parent = (BodyTube) tubes.getParent();
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final double maskedArea = tubes.getLength() * 2.0 * Math.PI * parent.getOuterRadius() / tubes.getFinCount();
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final double maskedArea = chord * 2.0 * Math.PI * bodyRadius / tubeCount;
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wettedArea = outerArea - maskedArea;
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log.debug("wetted area of tube fins " + wettedArea);
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// 2. frontal area of interstices between tubes for pressure drag calculation.
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// frontal area of interstices between tubes for pressure drag calculation.
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// We'll treat them as a closed blunt object.
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// area of disk passing through tube fin centers
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final double tubeDiskArea = Math.PI * MathUtil.pow2(bodyRadius + tubes.getOuterRadius());
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final double tubeDiskArea = Math.PI * MathUtil.pow2(bodyRadius + outerRadius);
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// half of combined area of tube fin exteriors. Deliberately using the outer radius here since we
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// calculate pressure drag from the tube walls in TubeCalc
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final double tubeOuterArea = tubes.getFinCount() * Math.PI * MathUtil.pow2(tubes.getOuterRadius()) / 2.0;
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final double tubeOuterArea = tubeCount * Math.PI * MathUtil.pow2(outerRadius) / 2.0;
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// body tube area
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final double bodyTubeArea = Math.PI * MathUtil.pow2(bodyRadius);
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// area of an interstice
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intersticeArea = (tubeDiskArea - tubeOuterArea - bodyTubeArea) / tubes.getFinCount();
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thickness = fin.getThickness();
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finCount = 3 * fin.getFinCount();
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baseRotation = fin.getBaseRotation();
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cantAngle = 0;
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span = 2 * fin.getOuterRadius();
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finArea = span * fin.getLength();
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crossSection = FinSet.CrossSection.SQUARE;
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calculateFinGeometry(fin);
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calculatePoly();
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interferenceFinCount = calculateInterferenceFinCount(fin);
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intersticeArea = (tubeDiskArea - tubeOuterArea - bodyTubeArea) / tubeCount;
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// Precompute most of CNa. Equation comes from Ribner, "The ring airfoil in nonaxial
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// flow", Journal of the Aeronautical Sciences 14(9) pp 529-530 (1947) equation (5).
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// As stated in techdoc.pdf, it's normalized by (1/2) rho v^2 (see section 3.1.1)
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final double arprime = 2 * ar / Math.PI;
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cnaconst = 2 * (arprime / (1 + arprime)) * Math.PI * Math.PI * innerRadius * chord;
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log.debug("ar " + ar + ", cnaconst " + cnaconst);
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}
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/*
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@ -144,8 +129,8 @@ public class TubeFinSetCalc extends TubeCalc {
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@Override
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public void calculateNonaxialForces(FlightConditions conditions, Transformation transform,
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AerodynamicForces forces, WarningSet warnings) {
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if (span < 0.001) {
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if (outerRadius < 0.001) {
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forces.setCm(0);
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forces.setCN(0);
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forces.setCNa(0);
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@ -158,111 +143,28 @@ public class TubeFinSetCalc extends TubeCalc {
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return;
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}
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// Add warnings (radius/2 == diameter/4)
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if( (0 < bodyRadius) && (thickness > bodyRadius / 2)){
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warnings.add(Warning.THICK_FIN);
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}
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//////// Calculate CNa. /////////
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// One fin without interference (both sub- and supersonic):
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double cna1 = calculateFinCNa1(conditions);
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// log.debug("Component cna1 = {}", cna1);
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// Multiple fins with fin-fin interference
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double cna;
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double theta = conditions.getTheta();
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double angle = baseRotation + transform.getXrotation();
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// Compute basic CNa without interference effects
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if (finCount == 1 || finCount == 2) {
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// Basic CNa from geometry
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double mul = 0;
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for (int i = 0; i < finCount; i++) {
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mul += MathUtil.pow2(Math.sin(theta - angle));
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angle += 2 * Math.PI / finCount;
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}
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cna = cna1 * mul;
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} else {
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// Basic CNa assuming full efficiency
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cna = cna1 * finCount / 2.0;
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}
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// log.debug("Component cna = {}", cna);
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// Take into account fin-fin interference effects
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switch (interferenceFinCount) {
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case 1:
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case 2:
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case 3:
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case 4:
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// No interference effect
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break;
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case 5:
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cna *= 0.948;
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break;
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case 6:
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cna *= 0.913;
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break;
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case 7:
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cna *= 0.854;
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break;
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case 8:
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cna *= 0.81;
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break;
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default:
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// Assume 75% efficiency
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cna *= 0.75;
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break;
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}
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// Body-fin interference effect
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double r = bodyRadius;
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double tau = r / (span + r);
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if (Double.isNaN(tau) || Double.isInfinite(tau))
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tau = 0;
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cna *= 1 + tau; // Classical Barrowman
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// cna *= pow2(1 + tau); // Barrowman thesis (too optimistic??)
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// log.debug("Component cna = {}", cna);
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// TODO: LOW: check for fin tip mach cone interference
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// (Barrowman thesis pdf-page 40)
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// TODO: LOW: fin-fin mach cone effect, MIL-HDBK page 5-25
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// Calculate CNa
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log.debug("body radius " + bodyRadius + ", ref area " + conditions.getRefArea());
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final double cna = cnaconst / conditions.getRefArea();
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// Calculate CP position
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double x = macLead + calculateCPPos(conditions) * macLength;
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// log.debug("Component macLead = {}", macLead);
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// log.debug("Component macLength = {}", macLength);
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// log.debug("Component x = {}", x);
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double x = calculateCPPos(conditions) * chord;
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// log.debug("CP position " + x);
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// Calculate roll forces, reduce forcing above stall angle
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// Without body-fin interference effect:
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// forces.CrollForce = fins * (macSpan+r) * cna1 * component.getCantAngle() /
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// conditions.getRefLength();
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// With body-fin interference effect:
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forces.setCrollForce(finCount * (macSpan + r) * cna1 * (1 + tau) * cantAngle / conditions.getRefLength());
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// Roll forces
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// This isn't really tested, since the cant angle is required to be 0.
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forces.setCrollForce((bodyRadius + outerRadius) * cna * cantAngle /
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conditions.getRefLength());
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if (conditions.getAOA() > STALL_ANGLE) {
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// System.out.println("Fin stalling in roll");
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forces.setCrollForce(forces.getCrollForce() * MathUtil.clamp(
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1 - (conditions.getAOA() - STALL_ANGLE) / (STALL_ANGLE / 2), 0, 1));
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// log.debug("Tube stalling in roll");
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forces.setCrollForce(forces.getCrollForce() *
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MathUtil.clamp(1 - (conditions.getAOA() - STALL_ANGLE) / (STALL_ANGLE / 2), 0, 1));
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}
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forces.setCrollDamp(calculateDampingMoment(conditions));
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forces.setCroll(forces.getCrollForce() - forces.getCrollDamp());
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forces.setCrollDamp((bodyRadius + outerRadius) * conditions.getRollRate()/conditions.getVelocity() * cna / conditions.getRefLength());
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// System.out.printf(component.getName() + ": roll rate:%.3f force:%.3f damp:%.3f " +
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// "total:%.3f\n",
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// conditions.getRollRate(), forces.CrollForce, forces.CrollDamp, forces.Croll);
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forces.setCroll(forces.getCrollForce() - forces.getCrollDamp());
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forces.setCNa(cna);
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forces.setCN(cna * MathUtil.min(conditions.getAOA(), STALL_ANGLE));
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@ -285,294 +187,8 @@ public class TubeFinSetCalc extends TubeCalc {
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// }
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forces.setCside(0);
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forces.setCyaw(0);
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}
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/**
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* Returns the MAC length of the fin. This is required in the friction drag
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* computation.
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*
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* @return the MAC length of the fin.
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*/
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public double getMACLength() {
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return macLength;
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}
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public double getMidchordPos() {
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return macLead + 0.5 * macLength;
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}
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/**
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* Pre-calculates the fin geometry values.
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*/
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protected void calculateFinGeometry(TubeFinSet component) {
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ar = 2 * pow2(span) / finArea;
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Coordinate[] points = {
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Coordinate.NUL,
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new Coordinate(0, span),
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new Coordinate(component.getLength(), span),
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new Coordinate(component.getLength(), 0)
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};
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// Calculate the chord lead and trail positions and length
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Arrays.fill(chordLead, Double.POSITIVE_INFINITY);
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Arrays.fill(chordTrail, Double.NEGATIVE_INFINITY);
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Arrays.fill(chordLength, 0);
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for (int point = 1; point < points.length; point++) {
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double x1 = points[point - 1].x;
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double y1 = points[point - 1].y;
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double x2 = points[point].x;
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double y2 = points[point].y;
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// Don't use the default EPSILON since it is too small
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// and causes too much numerical instability in the computation of x below
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if (MathUtil.equals(y1, y2, 0.001))
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continue;
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int i1 = (int) (y1 * 1.0001 / span * (DIVISIONS - 1));
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int i2 = (int) (y2 * 1.0001 / span * (DIVISIONS - 1));
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i1 = MathUtil.clamp(i1, 0, DIVISIONS - 1);
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i2 = MathUtil.clamp(i2, 0, DIVISIONS - 1);
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if (i1 > i2) {
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int tmp = i2;
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i2 = i1;
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i1 = tmp;
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}
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for (int i = i1; i <= i2; i++) {
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// Intersection point (x,y)
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double y = i * span / (DIVISIONS - 1);
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double x = (y - y2) / (y1 - y2) * x1 + (y1 - y) / (y1 - y2) * x2;
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if (x < chordLead[i])
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chordLead[i] = x;
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if (x > chordTrail[i])
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chordTrail[i] = x;
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// TODO: LOW: If fin point exactly on chord line, might be counted twice:
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if (y1 < y2) {
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chordLength[i] -= x;
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} else {
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chordLength[i] += x;
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}
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}
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}
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// Check and correct any inconsistencies
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for (int i = 0; i < DIVISIONS; i++) {
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if (Double.isInfinite(chordLead[i]) || Double.isInfinite(chordTrail[i]) ||
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Double.isNaN(chordLead[i]) || Double.isNaN(chordTrail[i])) {
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chordLead[i] = 0;
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chordTrail[i] = 0;
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}
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if (chordLength[i] < 0 || Double.isNaN(chordLength[i])) {
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chordLength[i] = 0;
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}
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if (chordLength[i] > chordTrail[i] - chordLead[i]) {
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chordLength[i] = chordTrail[i] - chordLead[i];
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}
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}
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/* Calculate fin properties:
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*
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* macLength // MAC length
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* macLead // MAC leading edge position
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* macSpan // MAC spanwise position
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* ar // Fin aspect ratio (already set)
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* span // Fin span (already set)
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*/
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macLength = 0;
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macLead = 0;
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macSpan = 0;
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cosGamma = 0;
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cosGammaLead = 0;
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rollSum = 0;
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double area = 0;
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double radius = component.getBodyRadius();
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final double dy = span / (DIVISIONS - 1);
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for (int i = 0; i < DIVISIONS; i++) {
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double length = chordTrail[i] - chordLead[i];
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double y = i * dy;
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macLength += length * length;
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log.debug("macLength = {}, length = {}, i = {}", macLength, length, i);
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macSpan += y * length;
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macLead += chordLead[i] * length;
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area += length;
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rollSum += chordLength[i] * pow2(radius + y);
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if (i > 0) {
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double dx = (chordTrail[i] + chordLead[i]) / 2 - (chordTrail[i - 1] + chordLead[i - 1]) / 2;
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cosGamma += dy / MathUtil.hypot(dx, dy);
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dx = chordLead[i] - chordLead[i - 1];
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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);
|
||||
|
||||
log.debug(forces.toString());
|
||||
}
|
||||
|
||||
/**
|
||||
@ -638,9 +254,9 @@ public class TubeFinSetCalc extends TubeCalc {
|
||||
@Override
|
||||
public double calculateFrictionCD(FlightConditions conditions, double componentCf, WarningSet warnings) {
|
||||
warnings.addAll(geometryWarnings);
|
||||
|
||||
|
||||
final double frictionCD = componentCf * wettedArea / conditions.getRefArea();
|
||||
log.debug("frictionCD " + frictionCD);
|
||||
|
||||
return frictionCD;
|
||||
}
|
||||
|
||||
@ -651,7 +267,6 @@ public class TubeFinSetCalc extends TubeCalc {
|
||||
warnings.addAll(geometryWarnings);
|
||||
final double cd = super.calculatePressureCD(conditions, stagnationCD, baseCD, warnings) +
|
||||
(stagnationCD + baseCD) * intersticeArea / conditions.getRefArea();
|
||||
log.debug("pressure CD " + cd);
|
||||
|
||||
return cd;
|
||||
}
|
||||
|
||||
Loading…
x
Reference in New Issue
Block a user