Needed to commit the new class
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JoePfeiffer
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core/src/net/sf/openrocket/simulation/AbstractEulerStepper.java
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184
core/src/net/sf/openrocket/simulation/AbstractEulerStepper.java
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package net.sf.openrocket.simulation;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import net.sf.openrocket.models.atmosphere.AtmosphericConditions;
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import net.sf.openrocket.rocketcomponent.InstanceMap;
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import net.sf.openrocket.rocketcomponent.RecoveryDevice;
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import net.sf.openrocket.simulation.exception.SimulationException;
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import net.sf.openrocket.util.Coordinate;
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import net.sf.openrocket.util.GeodeticComputationStrategy;
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import net.sf.openrocket.util.MathUtil;
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import net.sf.openrocket.util.WorldCoordinate;
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public abstract class AbstractEulerStepper extends AbstractSimulationStepper {
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private static final Logger log = LoggerFactory.getLogger(AbstractEulerStepper.class);
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private static final double RECOVERY_TIME_STEP = 0.5;
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protected double cd;
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@Override
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public SimulationStatus initialize(SimulationStatus status) {
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this.cd = computeCD(status);
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return status;
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}
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private double getCD() {
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return cd;
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}
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protected abstract double computeCD(SimulationStatus status);
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@Override
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public void step(SimulationStatus status, double maxTimeStep) throws SimulationException {
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// Get the atmospheric conditions
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AtmosphericConditions atmosphere = modelAtmosphericConditions(status);
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//// Local wind speed and direction
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Coordinate windSpeed = modelWindVelocity(status);
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Coordinate airSpeed = status.getRocketVelocity().add(windSpeed);
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// Compute drag force
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double mach = airSpeed.length() / atmosphere.getMachSpeed();
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double dynP = (0.5 * atmosphere.getDensity() * airSpeed.length2());
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double dragForce = getCD() * dynP * status.getConfiguration().getReferenceArea();
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// n.b. this is constant, and could be calculated once at the beginning of this simulation branch...
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double rocketMass = calculateStructureMass(status).getMass();
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double motorMass = calculateMotorMass(status).getMass();
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double mass = rocketMass + motorMass;
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// Compute drag acceleration
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Coordinate linearAcceleration;
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if (airSpeed.length() > 0.001) {
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linearAcceleration = airSpeed.normalize().multiply(-dragForce / mass);
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} else {
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linearAcceleration = Coordinate.NUL;
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}
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// Add effect of gravity
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double gravity = modelGravity(status);
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linearAcceleration = linearAcceleration.sub(0, 0, gravity);
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// Add coriolis acceleration
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Coordinate coriolisAcceleration = status.getSimulationConditions().getGeodeticComputation().getCoriolisAcceleration(
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status.getRocketWorldPosition(), status.getRocketVelocity());
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linearAcceleration = linearAcceleration.add(coriolisAcceleration);
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// Select tentative time step
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double timeStep = RECOVERY_TIME_STEP;
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// adjust based on change in acceleration (ie jerk)
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final double jerk = Math.abs(linearAcceleration.sub(status.getRocketAcceleration()).multiply(1.0/status.getPreviousTimeStep()).length());
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if (jerk > MathUtil.EPSILON) {
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timeStep = Math.min(timeStep, 1.0/jerk);
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}
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// but don't let it get *too* small
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timeStep = Math.max(timeStep, MIN_TIME_STEP);
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log.trace("timeStep is " + timeStep);
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// Perform Euler integration
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Coordinate newPosition = status.getRocketPosition().add(status.getRocketVelocity().multiply(timeStep)).
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add(linearAcceleration.multiply(MathUtil.pow2(timeStep) / 2));
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// If I've hit the ground, recalculate time step and position
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if (newPosition.z < 0) {
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final double a = linearAcceleration.z;
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final double v = status.getRocketVelocity().z;
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final double z0 = status.getRocketPosition().z;
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// The new timestep is the solution of
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// 1/2 at^2 + vt + z0 = 0
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timeStep = (-v - Math.sqrt(v*v - 2*a*z0))/a;
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log.trace("ground hit changes timeStep to " + timeStep);
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newPosition = status.getRocketPosition().add(status.getRocketVelocity().multiply(timeStep)).
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add(linearAcceleration.multiply(MathUtil.pow2(timeStep) / 2));
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// avoid rounding error in new altitude
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newPosition = newPosition.setZ(0);
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}
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status.setSimulationTime(status.getSimulationTime() + timeStep);
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status.setPreviousTimeStep(timeStep);
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status.setRocketPosition(newPosition);
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status.setRocketVelocity(status.getRocketVelocity().add(linearAcceleration.multiply(timeStep)));
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status.setRocketAcceleration(linearAcceleration);
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// Update the world coordinate
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WorldCoordinate w = status.getSimulationConditions().getLaunchSite();
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w = status.getSimulationConditions().getGeodeticComputation().addCoordinate(w, status.getRocketPosition());
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status.setRocketWorldPosition(w);
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// Store data
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FlightDataBranch data = status.getFlightData();
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boolean extra = status.getSimulationConditions().isCalculateExtras();
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data.addPoint();
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data.setValue(FlightDataType.TYPE_TIME, status.getSimulationTime());
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data.setValue(FlightDataType.TYPE_ALTITUDE, status.getRocketPosition().z);
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data.setValue(FlightDataType.TYPE_POSITION_X, status.getRocketPosition().x);
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data.setValue(FlightDataType.TYPE_POSITION_Y, status.getRocketPosition().y);
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airSpeed = status.getRocketVelocity().add(windSpeed);
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if (extra) {
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data.setValue(FlightDataType.TYPE_POSITION_XY,
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MathUtil.hypot(status.getRocketPosition().x, status.getRocketPosition().y));
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data.setValue(FlightDataType.TYPE_POSITION_DIRECTION,
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Math.atan2(status.getRocketPosition().y, status.getRocketPosition().x));
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data.setValue(FlightDataType.TYPE_VELOCITY_XY,
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MathUtil.hypot(status.getRocketVelocity().x, status.getRocketVelocity().y));
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data.setValue(FlightDataType.TYPE_ACCELERATION_XY,
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MathUtil.hypot(linearAcceleration.x, linearAcceleration.y));
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data.setValue(FlightDataType.TYPE_ACCELERATION_TOTAL, linearAcceleration.length());
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double Re = airSpeed.length() *
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status.getConfiguration().getLengthAerodynamic() /
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atmosphere.getKinematicViscosity();
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data.setValue(FlightDataType.TYPE_REYNOLDS_NUMBER, Re);
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}
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data.setValue(FlightDataType.TYPE_LATITUDE, status.getRocketWorldPosition().getLatitudeRad());
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data.setValue(FlightDataType.TYPE_LONGITUDE, status.getRocketWorldPosition().getLongitudeRad());
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data.setValue(FlightDataType.TYPE_GRAVITY, gravity);
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if (status.getSimulationConditions().getGeodeticComputation() != GeodeticComputationStrategy.FLAT) {
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data.setValue(FlightDataType.TYPE_CORIOLIS_ACCELERATION, coriolisAcceleration.length());
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}
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data.setValue(FlightDataType.TYPE_VELOCITY_Z, status.getRocketVelocity().z);
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data.setValue(FlightDataType.TYPE_ACCELERATION_Z, linearAcceleration.z);
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data.setValue(FlightDataType.TYPE_VELOCITY_TOTAL, airSpeed.length());
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data.setValue(FlightDataType.TYPE_MACH_NUMBER, mach);
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data.setValue(FlightDataType.TYPE_MASS, mass);
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data.setValue(FlightDataType.TYPE_MOTOR_MASS, motorMass);
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data.setValue(FlightDataType.TYPE_THRUST_FORCE, 0);
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data.setValue(FlightDataType.TYPE_DRAG_FORCE, dragForce);
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data.setValue(FlightDataType.TYPE_WIND_VELOCITY, windSpeed.length());
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data.setValue(FlightDataType.TYPE_AIR_TEMPERATURE, atmosphere.getTemperature());
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data.setValue(FlightDataType.TYPE_AIR_PRESSURE, atmosphere.getPressure());
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data.setValue(FlightDataType.TYPE_SPEED_OF_SOUND, atmosphere.getMachSpeed());
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data.setValue(FlightDataType.TYPE_TIME_STEP, timeStep);
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data.setValue(FlightDataType.TYPE_COMPUTATION_TIME,
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(System.nanoTime() - status.getSimulationStartWallTime()) / 1000000000.0);
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log.trace("time " + data.getLast(FlightDataType.TYPE_TIME) + ", altitude " + data.getLast(FlightDataType.TYPE_ALTITUDE) + ", velocity " + data.getLast(FlightDataType.TYPE_VELOCITY_Z));
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}
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}
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