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Add unit test

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This commit is contained in:
JoePfeiffer 2022-12-17 10:40:31 -07:00
parent 8fd3e58693
commit 955f00c877
2 changed files with 106 additions and 4 deletions
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9
core/src/net/sf/openrocket/aerodynamics/barrowman/RailButtonCalc.java
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@ -47,8 +47,8 @@ public class RailButtonCalc extends RocketComponentCalc {
@Override
public double calculatePressureCD(FlightConditions conditions,
double stagnationCD, double baseCD, WarningSet warnings) {
// grab relevant button params
final int instanceCount = button.getInstanceCount();
final Coordinate[] instanceOffsets = button.getInstanceOffsets();
@ -65,10 +65,10 @@ public class RailButtonCalc extends RocketComponentCalc {
// compute boundary layer height at button location. I can't find a good reference for the
// formula, e.g. https://aerospaceengineeringblog.com/boundary-layers/ simply says it's the
// "scientific consensus".
double x = (button.toAbsolute(instanceOffsets[i]))[0].x; // location of button
double x = (button.toAbsolute(instanceOffsets[i]))[0].x; // location of button
double rex = calculateReynoldsNumber(x, conditions); // Reynolds number of button location
double del = 0.37 * x / Math.pow(rex, 0.2); // Boundary layer thickness
// compute mean airspeed over button
// this assumes airspeed changes linearly through boundary layer
// and that all parts of the railbutton contribute equally to Cd,
@ -96,6 +96,7 @@ public class RailButtonCalc extends RocketComponentCalc {
// add to CDmul
CDmul += cd;
}
return CDmul*stagnationCD * refArea / conditions.getRefArea();
return CDmul * stagnationCD * refArea / conditions.getRefArea();
}
}

101
core/test/net/sf/openrocket/aerodynamics/RailButtonCalcTest.java Normal file
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@ -0,0 +1,101 @@
package net.sf.openrocket.aerodynamics;
import static org.junit.Assert.assertEquals;
import org.junit.BeforeClass;
import org.junit.Test;
import com.google.inject.Guice;
import com.google.inject.Injector;
import com.google.inject.Module;
import net.sf.openrocket.ServicesForTesting;
import net.sf.openrocket.aerodynamics.BarrowmanCalculator;
import net.sf.openrocket.aerodynamics.barrowman.RailButtonCalc;
import net.sf.openrocket.plugin.PluginModule;
import net.sf.openrocket.rocketcomponent.FlightConfiguration;
import net.sf.openrocket.rocketcomponent.BodyTube;
import net.sf.openrocket.rocketcomponent.RailButton;
import net.sf.openrocket.rocketcomponent.LaunchLug;
import net.sf.openrocket.rocketcomponent.Rocket;
import net.sf.openrocket.rocketcomponent.position.AxialMethod;
import net.sf.openrocket.startup.Application;
import net.sf.openrocket.util.MathUtil;
import net.sf.openrocket.util.TestRockets;
import net.sf.openrocket.util.Transformation;
public class RailButtonCalcTest {
protected final double EPSILON = 0.0001;
private static Injector injector;
@BeforeClass
public static void setup() {
Module applicationModule = new ServicesForTesting();
Module pluginModule = new PluginModule();
injector = Guice.createInjector( applicationModule, pluginModule);
Application.setInjector(injector);
}
@Test
public void testRailButtons() {
Rocket rocket = TestRockets.makeEstesAlphaIII();
FlightConfiguration config = rocket.getSelectedConfiguration();
// Get the body tube...
BodyTube tube = (BodyTube)rocket.getChild(0).getChild(1);
// Replace the launch lug with a (single) railbutton
LaunchLug lug = (LaunchLug)tube.getChild(1);
rocket.removeChild(lug);
RailButton button = new RailButton();
tube.addChild(button);
// Button parameters from Binder Design standard 1010
button.setOuterDiameter(0.011);
button.setInnerDiameter(0.006);
button.setBaseHeight(0.002);
button.setFlangeHeight(0.002);
button.setTotalHeight(0.008);
button.setAxialMethod(AxialMethod.ABSOLUTE);
button.setAxialOffset(1.0);
// Set up flight conditions
FlightConditions conditions = new FlightConditions(config);
conditions.setMach(1.0);
BarrowmanCalculator barrowmanObj = new BarrowmanCalculator();
RailButtonCalc calcObj = new RailButtonCalc(button);
// Calculate effective CD for rail button
// Boundary layer height
double rex = calcObj.calculateReynoldsNumber(1.0, conditions); // Reynolds number of button location
double del = 0.37 * 1.0 / Math.pow(rex, 0.2); // Boundary layer height
// Interpolate velocity at midpoint of railbutton
double mach = MathUtil.map(0.008/2.0, 0, del, 0, 1.0);
// Interpolate to get CD
double cd = MathUtil.map(mach, 0.2, 0.3, 1.22, 1.25);
// Reference area of rail button
final double outerArea = button.getTotalHeight() * button.getOuterDiameter();
final double notchArea = (button.getOuterDiameter() - button.getInnerDiameter()) * button.getInnerHeight();
final double refArea = outerArea - notchArea;
// Get "effective" CD
double calccd = cd * MathUtil.pow2(mach) * barrowmanObj.calculateStagnationCD(conditions.getMach()) * refArea / conditions.getRefArea() ;
// Now compare with value from RailButtonCalc
WarningSet warnings = new WarningSet();
AerodynamicForces assemblyForces = new AerodynamicForces().zero();
AerodynamicForces componentForces = new AerodynamicForces();
double testcd = calcObj.calculatePressureCD(conditions, barrowmanObj.calculateStagnationCD(conditions.getMach()), 0, warnings);
assertEquals("Calculated rail button CD incorrect", calccd, testcd, EPSILON);
}
}