move Reynolds number and friction coefficient to separate methods for readability
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JoePfeiffer
parent
4fd3f26c9e
commit
5c62ad725a
@ -324,108 +324,14 @@ public class BarrowmanCalculator extends AbstractAerodynamicCalculator {
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*/
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private double calculateFrictionCD(FlightConfiguration configuration, FlightConditions conditions,
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Map<RocketComponent, AerodynamicForces> map, WarningSet set) {
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double c1 = 1.0, c2 = 1.0;
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double mach = conditions.getMach();
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double Re;
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double Cf;
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double Re = calculateReynoldsNumber(configuration, conditions);
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double Cf = calculateFrictionCoefficient(configuration, mach, Re);
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double roughnessCorrection = calculateRoughnessCorrection(mach);
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if (calcMap == null)
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buildCalcMap(configuration);
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Re = conditions.getVelocity() * configuration.getLength() /
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conditions.getAtmosphericConditions().getKinematicViscosity();
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// Calculate the skin friction coefficient (assume non-roughness limited)
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if (configuration.getRocket().isPerfectFinish()) {
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// Assume partial laminar layer. Roughness-limitation is checked later.
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if (Re < 1e4) {
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// Too low, constant
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Cf = 1.33e-2;
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} else if (Re < 5.39e5) {
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// Fully laminar
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Cf = 1.328 / MathUtil.safeSqrt(Re);
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} else {
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// Transitional
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Cf = 1.0 / pow2(1.50 * Math.log(Re) - 5.6) - 1700 / Re;
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}
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// Compressibility correction
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if (mach < 1.1) {
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// Below Re=1e6 no correction
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if (Re > 1e6) {
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if (Re < 3e6) {
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c1 = 1 - 0.1 * pow2(mach) * (Re - 1e6) / 2e6; // transition to turbulent
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} else {
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c1 = 1 - 0.1 * pow2(mach);
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}
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}
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}
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if (mach > 0.9) {
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if (Re > 1e6) {
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if (Re < 3e6) {
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c2 = 1 + (1.0 / Math.pow(1 + 0.045 * pow2(mach), 0.25) - 1) * (Re - 1e6) / 2e6;
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} else {
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c2 = 1.0 / Math.pow(1 + 0.045 * pow2(mach), 0.25);
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}
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}
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}
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// Applying continuously around Mach 1
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if (mach < 0.9) {
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Cf *= c1;
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} else if (mach < 1.1) {
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Cf *= (c2 * (mach - 0.9) / 0.2 + c1 * (1.1 - mach) / 0.2);
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} else {
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Cf *= c2;
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}
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} else {
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// Assume fully turbulent. Roughness-limitation is checked later.
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if (Re < 1e4) {
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// Too low, constant
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Cf = 1.48e-2;
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} else {
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// Turbulent
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Cf = 1.0 / pow2(1.50 * Math.log(Re) - 5.6);
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}
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// Compressibility correction
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if (mach < 1.1) {
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c1 = 1 - 0.1 * pow2(mach);
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}
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if (mach > 0.9) {
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c2 = 1 / Math.pow(1 + 0.15 * pow2(mach), 0.58);
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}
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// Applying continuously around Mach 1
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if (mach < 0.9) {
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Cf *= c1;
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} else if (mach < 1.1) {
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Cf *= c2 * (mach - 0.9) / 0.2 + c1 * (1.1 - mach) / 0.2;
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} else {
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Cf *= c2;
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}
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}
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// Roughness-limited value correction term
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double roughnessCorrection;
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if (mach < 0.9) {
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roughnessCorrection = 1 - 0.1 * pow2(mach);
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} else if (mach > 1.1) {
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roughnessCorrection = 1 / (1 + 0.18 * pow2(mach));
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} else {
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c1 = 1 - 0.1 * pow2(0.9);
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c2 = 1.0 / (1 + 0.18 * pow2(1.1));
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roughnessCorrection = c2 * (mach - 0.9) / 0.2 + c1 * (1.1 - mach) / 0.2;
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}
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/*
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* Calculate the friction drag coefficient.
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@ -445,11 +351,6 @@ public class BarrowmanCalculator extends AbstractAerodynamicCalculator {
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final InstanceMap imap = configuration.getActiveInstances();
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for(Map.Entry<RocketComponent, ArrayList<InstanceContext>> entry: imap.entrySet() ) {
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final RocketComponent c = entry.getKey();
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// Consider only SymmetricComponents and FinSets:
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if (!(c instanceof SymmetricComponent) &&
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!(c instanceof FinSet))
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continue;
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// iterate across component instances
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final ArrayList<InstanceContext> contextList = entry.getValue();
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@ -542,7 +443,134 @@ public class BarrowmanCalculator extends AbstractAerodynamicCalculator {
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return (finFriction + correction * bodyFriction) / conditions.getRefArea();
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}
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/**
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* Calculation of Reynolds Number
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*
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* @param configuration Rocket configuration
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* @param conditions Flight conditions taken into account
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* @return Reynolds Number
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*/
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private double calculateReynoldsNumber(FlightConfiguration configuration, FlightConditions conditions) {
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return conditions.getVelocity() * configuration.getLength() /
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conditions.getAtmosphericConditions().getKinematicViscosity();
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}
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/**
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* Calculation of skin friction coefficient
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*
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*
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* return skin friction coefficient
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*/
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private double calculateFrictionCoefficient(FlightConfiguration configuration, double mach, double Re) {
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double Cf;
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double c1 = 1.0, c2 = 1.0;
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// Calculate the skin friction coefficient (assume non-roughness limited)
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if (configuration.getRocket().isPerfectFinish()) {
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// Assume partial laminar layer. Roughness-limitation is checked later.
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if (Re < 1e4) {
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// Too low, constant
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Cf = 1.33e-2;
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} else if (Re < 5.39e5) {
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// Fully laminar
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Cf = 1.328 / MathUtil.safeSqrt(Re);
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} else {
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// Transitional
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Cf = 1.0 / pow2(1.50 * Math.log(Re) - 5.6) - 1700 / Re;
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}
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// Compressibility correction
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if (mach < 1.1) {
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// Below Re=1e6 no correction
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if (Re > 1e6) {
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if (Re < 3e6) {
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c1 = 1 - 0.1 * pow2(mach) * (Re - 1e6) / 2e6; // transition to turbulent
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} else {
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c1 = 1 - 0.1 * pow2(mach);
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}
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}
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}
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if (mach > 0.9) {
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if (Re > 1e6) {
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if (Re < 3e6) {
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c2 = 1 + (1.0 / Math.pow(1 + 0.045 * pow2(mach), 0.25) - 1) * (Re - 1e6) / 2e6;
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} else {
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c2 = 1.0 / Math.pow(1 + 0.045 * pow2(mach), 0.25);
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}
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}
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}
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// Applying continuously around Mach 1
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if (mach < 0.9) {
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Cf *= c1;
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} else if (mach < 1.1) {
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Cf *= (c2 * (mach - 0.9) / 0.2 + c1 * (1.1 - mach) / 0.2);
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} else {
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Cf *= c2;
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}
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} else {
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// Assume fully turbulent. Roughness-limitation is checked later.
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if (Re < 1e4) {
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// Too low, constant
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Cf = 1.48e-2;
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} else {
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// Turbulent
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Cf = 1.0 / pow2(1.50 * Math.log(Re) - 5.6);
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}
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// Compressibility correction
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if (mach < 1.1) {
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c1 = 1 - 0.1 * pow2(mach);
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}
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if (mach > 0.9) {
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c2 = 1 / Math.pow(1 + 0.15 * pow2(mach), 0.58);
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}
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// Applying continuously around Mach 1
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if (mach < 0.9) {
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Cf *= c1;
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} else if (mach < 1.1) {
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Cf *= c2 * (mach - 0.9) / 0.2 + c1 * (1.1 - mach) / 0.2;
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} else {
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Cf *= c2;
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}
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}
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return Cf;
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}
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/**
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* Calculation of correction for roughness
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*
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* @param mach
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* @return roughness correction
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**/
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private double calculateRoughnessCorrection(double mach) {
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double c1, c2;
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// Roughness-limited value correction term
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double roughnessCorrection;
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if (mach < 0.9) {
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roughnessCorrection = 1 - 0.1 * pow2(mach);
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} else if (mach > 1.1) {
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roughnessCorrection = 1 / (1 + 0.18 * pow2(mach));
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} else {
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c1 = 1 - 0.1 * pow2(0.9);
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c2 = 1.0 / (1 + 0.18 * pow2(1.1));
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roughnessCorrection = c2 * (mach - 0.9) / 0.2 + c1 * (1.1 - mach) / 0.2;
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}
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return roughnessCorrection;
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}
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/**
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* Calculation of drag coefficient due to pressure
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