Merge pull request #2119 from JoePfeiffer/fix-base-drag-take-2

Fix base drag

core/src/net/sf/openrocket/aerodynamics/BarrowmanCalculator.java

@@ -760,6 +760,12 @@ public class BarrowmanCalculator extends AbstractAerodynamicCalculator {
 				continue;
 			}
 
+			
+			if (c.isCDOverridden() ||
+				c.isCDOverriddenByAncestor()) {
+				continue;
+			}
+			
 			SymmetricComponent s = (SymmetricComponent) c;
 			double foreRadius = s.getForeRadius();
 			double aftRadius = s.getAftRadius();
@@ -771,34 +777,19 @@ public class BarrowmanCalculator extends AbstractAerodynamicCalculator {
 
 			int instanceCount = entry.getValue().size();
 
-			if (c.isCDOverridden() ||
+			// get forward radius of next component
-				c.isCDOverriddenByAncestor()) {
+			final SymmetricComponent nextComponent = s.getNextSymmetricComponent();
-				continue;
+			double nextRadius;
+			if ((nextComponent != null) && configuration.isComponentActive(nextComponent)) {
+				nextRadius = nextComponent.getForeRadius();
+			} else {
+				nextRadius = 0.0;
 			}
 
-			// if aft radius of previous component is greater than my forward radius, set
+			// if fore radius of next component is less than my aft radius, set my
-			// its aft CD
+			// base CD
-			double radius = 0;
+			if (nextRadius < aftRadius) {
-			final SymmetricComponent prevComponent = s.getPreviousSymmetricComponent();
+				double area = Math.PI * (pow2(aftRadius) - pow2(nextRadius));
-			if (prevComponent != null && configuration.isComponentActive(prevComponent)) {
-				radius = prevComponent.getAftRadius();
-			}
-			
-			if (radius > foreRadius) {
-				double area = Math.PI * (pow2(radius) - pow2(foreRadius));
-				double cd = base * area / conditions.getRefArea();
-				total += instanceCount * cd;
-				if ((forceMap != null) && (prevComponent != null)) {
-					forceMap.get(prevComponent).setBaseCD(cd);
-				}
-			}
-				
-			// if I'm the last component, set my base CD
-			// note:  the iterator *should* serve up the next component.... buuuut ....
-			//        this code is tested, and there's no compelling reason to change.
-			final SymmetricComponent n = s.getNextSymmetricComponent();
-			if ((n == null) || !configuration.isStageActive(n.getStageNumber())) {
-				double area = Math.PI * pow2(aftRadius);
 				double cd = base * area / conditions.getRefArea();
 				total += instanceCount * cd;
 				if (forceMap != null) {

core/test/net/sf/openrocket/aerodynamics/BarrowmanCalculatorTest.java

@@ -499,6 +499,77 @@ public class BarrowmanCalculatorTest {
 		assertEquals("should be warning from podset airframe overlap", 1, warnings.size());
 	}
 
+	@Test
+	public void testBaseDragWithOverride() {
+		final WarningSet warnings = new WarningSet();
+		final BarrowmanCalculator calc = new BarrowmanCalculator();
+		
+		// get base drag of minimal rocket consisting of just a tube.
+		final Rocket tubeRocket = new Rocket();
+		final AxialStage tubeStage = new AxialStage();
+		tubeRocket.addChild(tubeStage);
+		
+		final BodyTube tubeBodyTube = new BodyTube();
+		tubeStage.addChild(tubeBodyTube);
+
+		final FlightConfiguration tubeConfig = new FlightConfiguration(tubeRocket);
+		final FlightConditions tubeConditions = new FlightConditions(tubeConfig);
+		final AerodynamicForces tubeForces = calc.getAerodynamicForces(tubeConfig, tubeConditions, warnings);
+		final double tubeBaseCD = tubeForces.getBaseCD();
+
+		// get base CD of minimal rocket consisting of just a cone
+		final Rocket coneRocket = new Rocket();
+		final AxialStage coneStage = new AxialStage();
+		coneRocket.addChild(coneStage);
+
+		NoseCone coneCone = new NoseCone();
+		coneCone.setAftRadius(tubeBodyTube.getOuterRadius());
+		coneStage.addChild(coneCone);
+
+		final FlightConfiguration coneConfig = new FlightConfiguration(coneRocket);
+		final FlightConditions coneConditions = new FlightConditions(coneConfig);
+		final AerodynamicForces coneForces = calc.getAerodynamicForces(coneConfig, coneConditions, warnings);
+		final double coneBaseCD = coneForces.getBaseCD();
+
+		// now our test rocket, with a tube and a cone
+		final Rocket testRocket = new Rocket();
+		final AxialStage testStage = new AxialStage();
+		testRocket.addChild(testStage);
+
+		final BodyTube testTube = new BodyTube();
+		testTube.setOuterRadius(tubeBodyTube.getOuterRadius());
+		testStage.addChild(testTube);
+
+		final NoseCone testCone = new NoseCone();
+		testCone.setAftRadius(coneCone.getAftRadius());
+		testStage.addChild(testCone);
+
+		FlightConfiguration testConfig = new FlightConfiguration(testRocket);
+		FlightConditions testConditions = new FlightConditions(testConfig);
+
+		// no overrides
+		AerodynamicForces testForces = calc.getAerodynamicForces(testConfig, testConditions, warnings);
+		assertEquals("base CD should be base CD of tube plus base CD of cone", tubeBaseCD + coneBaseCD, testForces.getBaseCD(), EPSILON);
+
+		// override tube CD
+		testTube.setCDOverridden(true);
+		testTube.setOverrideCD(0);
+		testForces = calc.getAerodynamicForces(testConfig, testConditions, warnings);
+		assertEquals("base CD should be base CD of cone", coneBaseCD, testForces.getBaseCD(), EPSILON);
+
+		// override cone CD
+		testCone.setCDOverridden(true);
+		testCone.setOverrideCD(0);
+		testForces = calc.getAerodynamicForces(testConfig, testConditions, warnings);
+		assertEquals("base CD should be 0", 0.0, testForces.getBaseCD(), EPSILON);
+
+
+		// and turn off tube override
+		testTube.setCDOverridden(false);
+		testForces = calc.getAerodynamicForces(testConfig, testConditions, warnings);
+		assertEquals("base CD should be base CD of tube", tubeBaseCD, testForces.getBaseCD(), EPSILON);
+	}
+
 	/**
 	 * Tests railbutton drag.  Really is testing instancing more than actual drag calculations, and making
 	 * sure we don't divide by 0 when not moving