diff --git a/core/resources/l10n/messages.properties b/core/resources/l10n/messages.properties index 8fbf01f50..95b8960d0 100644 --- a/core/resources/l10n/messages.properties +++ b/core/resources/l10n/messages.properties @@ -1789,7 +1789,6 @@ 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. diff --git a/core/src/net/sf/openrocket/aerodynamics/Warning.java b/core/src/net/sf/openrocket/aerodynamics/Warning.java index 0653b1a3e..bda67ed61 100644 --- a/core/src/net/sf/openrocket/aerodynamics/Warning.java +++ b/core/src/net/sf/openrocket/aerodynamics/Warning.java @@ -392,7 +392,6 @@ 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")); } diff --git a/core/src/net/sf/openrocket/aerodynamics/barrowman/TubeFinSetCalc.java b/core/src/net/sf/openrocket/aerodynamics/barrowman/TubeFinSetCalc.java index 052d5e785..88e402f1d 100644 --- a/core/src/net/sf/openrocket/aerodynamics/barrowman/TubeFinSetCalc.java +++ b/core/src/net/sf/openrocket/aerodynamics/barrowman/TubeFinSetCalc.java @@ -25,52 +25,32 @@ 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. - * - * @author kruland * */ public class TubeFinSetCalc extends TubeCalc { - private final static Logger log = LoggerFactory.getLogger(TubeFinSetCalc.class); - - final double intersticeArea; private static final double STALL_ANGLE = (20 * Math.PI / 180); + private final double[] poly = new double[6]; - /** Number of divisions in the fin chords. */ - protected static final int DIVISIONS = 48; + // parameters straight from configuration; we'll be grabbing them once + // so code is a bit shorter elsewhere + private final double bodyRadius; + private final double chord; + private final double innerRadius; + private final double outerRadius; + private final int tubeCount; + private final double baseRotation; + // at present tubes are only allowed a cant angle of 0 + private final double cantAngle; - 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]; + // values we can precompute once + private final double ar; + private final double intersticeArea; + private final double wettedArea; + private final double cnaconst; protected final WarningSet geometryWarnings = new WarningSet(); - - private final double[] poly = new double[6]; - - private final double wettedArea; - - 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; public TubeFinSetCalc(RocketComponent component) { super(component); @@ -79,62 +59,67 @@ public class TubeFinSetCalc extends TubeCalc { } 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); } + bodyRadius = tubes.getBodyRadius(); + chord = tubes.getLength(); + innerRadius = tubes.getInnerRadius(); + outerRadius = tubes.getOuterRadius(); + tubeCount = tubes.getFinCount(); + baseRotation = tubes.getBaseRotation(); + // at present, tube cant angle can only be 0 + cantAngle = 0; + // cantAngle = tubes.getCantAngle(); + // precompute geometry. This will be the geometry of a single tube, since BarrowmanCalculator // iterates across them. Doesn't consider interference between them; that should only be relevant for // fins that are either separated or overlapping. - bodyRadius = tubes.getBodyRadius(); - // 1. wetted area for friction drag calculation. We don't consider the inner surface of the tube; + // aspect ratio. + ar = 2 * innerRadius / chord; + + // wetted area for friction drag calculation. We don't consider the inner surface of the tube; // that affects the pressure drop through the tube and so (indirecctly) affects the pressure drag. // 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 the other half of the area - final double outerArea = tubes.getLength() * Math.PI * tubes.getOuterRadius(); + // body tube, only consider the other half of the area (so only multiplying by pi instead of 2*pi) + final double outerArea = chord * Math.PI * outerRadius; // Surface area of the portion of the body tube masked by the tube fins, per tube final BodyTube parent = (BodyTube) tubes.getParent(); - final double maskedArea = tubes.getLength() * 2.0 * Math.PI * parent.getOuterRadius() / tubes.getFinCount(); + final double maskedArea = chord * 2.0 * Math.PI * bodyRadius / tubeCount; wettedArea = outerArea - maskedArea; log.debug("wetted area of tube fins " + wettedArea); - // 2. frontal area of interstices between tubes for pressure drag calculation. + // frontal area of interstices between tubes for pressure drag calculation. // We'll treat them as a closed blunt object. // area of disk passing through tube fin centers - final double tubeDiskArea = Math.PI * MathUtil.pow2(bodyRadius + tubes.getOuterRadius()); + final double tubeDiskArea = Math.PI * MathUtil.pow2(bodyRadius + outerRadius); // half of combined area of tube fin exteriors. Deliberately using the outer radius here since we // calculate pressure drag from the tube walls in TubeCalc - final double tubeOuterArea = tubes.getFinCount() * Math.PI * MathUtil.pow2(tubes.getOuterRadius()) / 2.0; + final double tubeOuterArea = tubeCount * Math.PI * MathUtil.pow2(outerRadius) / 2.0; // body tube area final double bodyTubeArea = Math.PI * MathUtil.pow2(bodyRadius); // area of an interstice - intersticeArea = (tubeDiskArea - tubeOuterArea - bodyTubeArea) / tubes.getFinCount(); - - thickness = fin.getThickness(); - 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); + intersticeArea = (tubeDiskArea - tubeOuterArea - bodyTubeArea) / tubeCount; + + // Precompute most of CNa. Equation comes from Ribner, "The ring airfoil in nonaxial + // flow", Journal of the Aeronautical Sciences 14(9) pp 529-530 (1947) equation (5). + // As stated in techdoc.pdf, it's normalized by (1/2) rho v^2 (see section 3.1.1) + final double arprime = 2 * ar / Math.PI; + cnaconst = 2 * (arprime / (1 + arprime)) * Math.PI * Math.PI * innerRadius * chord; + log.debug("ar " + ar + ", cnaconst " + cnaconst); } /* @@ -144,8 +129,8 @@ public class TubeFinSetCalc extends TubeCalc { @Override public void calculateNonaxialForces(FlightConditions conditions, Transformation transform, AerodynamicForces forces, WarningSet warnings) { - - if (span < 0.001) { + + if (outerRadius < 0.001) { forces.setCm(0); forces.setCN(0); forces.setCNa(0); @@ -158,111 +143,28 @@ public class TubeFinSetCalc extends TubeCalc { return; } - // Add warnings (radius/2 == diameter/4) - if( (0 < bodyRadius) && (thickness > bodyRadius / 2)){ - warnings.add(Warning.THICK_FIN); - } - - //////// 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 CNa + log.debug("body radius " + bodyRadius + ", ref area " + conditions.getRefArea()); + final double cna = cnaconst / conditions.getRefArea(); // Calculate CP position - double x = macLead + calculateCPPos(conditions) * macLength; - // log.debug("Component macLead = {}", macLead); - // log.debug("Component macLength = {}", macLength); - // log.debug("Component x = {}", x); + double x = calculateCPPos(conditions) * chord; + // log.debug("CP position " + 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()); + // Roll forces + // This isn't really tested, since the cant angle is required to be 0. + forces.setCrollForce((bodyRadius + outerRadius) * cna * 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)); + // log.debug("Tube 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()); + + forces.setCrollDamp((bodyRadius + outerRadius) * conditions.getRollRate()/conditions.getVelocity() * cna / conditions.getRefLength()); - // System.out.printf(component.getName() + ": roll rate:%.3f force:%.3f damp:%.3f " + - // "total:%.3f\n", - // conditions.getRollRate(), forces.CrollForce, forces.CrollDamp, forces.Croll); + forces.setCroll(forces.getCrollForce() - forces.getCrollDamp()); forces.setCNa(cna); forces.setCN(cna * MathUtil.min(conditions.getAOA(), STALL_ANGLE)); @@ -285,294 +187,8 @@ public class TubeFinSetCalc extends TubeCalc { // } 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); + + 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; }