def forceFromCoefficients(rocketState, environment, Cd, Cl, CMx, CMy, CMz,
CPLocation, refArea, refLength):
''' Initialize ForceMomentSystem from all aerodynamic coefficients '''
q = AeroParameters.getDynamicPressure(rocketState, environment)
if q == 0.0:
# No force without dynamic pressure
return ForceMomentSystem(Vector(0, 0, 0))
nonDimConstant = q * refArea
#### Drag ####
localFrameAirVel = AeroParameters.getLocalFrameAirVel(
rocketState, environment)
dragDirection = localFrameAirVel.normalize()
dragForce = dragDirection * Cd
#### Lift ####
# Find the lift force direction
# Lift force will be in the same plane as the normalForceDirection & rocketFrameAirVel vectors
# But, the lift force will be perpendicular to rocketFraeAirVel, whereas the normalForceDirection might form an acute angle with it
# Rotate the normal force direction vector until it's perpendicular with rocketFrameAirVel
normalForceDir = AeroParameters.getNormalAeroForceDirection(
rocketState, environment)
rotAxis = localFrameAirVel.crossProduct(normalForceDir)
angle = math.pi / 2 - localFrameAirVel.angle(normalForceDir)
rotatorQuat = Quaternion(rotAxis, angle)
liftDirection = rotatorQuat.rotate(normalForceDir)
liftForce = liftDirection * Cl
# Combine and redimensionalize
totalForce = (dragForce + liftForce) * nonDimConstant
#### Moments ####
moments = Vector(CMx, CMy, CMz) * nonDimConstant * refLength
return ForceMomentSystem(totalForce, CPLocation, moments)
def forceFromCdCN(rocketState,
environment,
Cd,
CN,
CPLocation,
refArea,
moment=None):
'''
Convenience function for Barrowman Aero methods
Initialize ForceMomentSystem from aerodynamic coefficients Cd and CN
Cd should NOT already be adjusted for angle of attack
Moment should be a dimensional moment vector
'''
angleOfAttack = AeroParameters.getTotalAOA(rocketState, environment)
q = AeroParameters.getDynamicPressure(rocketState, environment)
#### Axial Force ####
CA = getDragToAxialForceFactor(angleOfAttack) * Cd
axialForce = Vector(0, 0, -CA) #Axial force is in the negative Z-direction
#### Normal Force ####
normalForce = AeroParameters.getNormalAeroForceDirection(
rocketState, environment) * CN
totalForce = (axialForce + normalForce) * refArea * q
return ForceMomentSystem(totalForce, CPLocation, moment)
def test_getNormalAeroForceDirection(self):
zeroAngVel = AngularVelocity(0,0,0)
zeroPos = Vector(0,0,0)
state1 = RigidBodyState(zeroPos, self.dummyVelocity1, self.dummyOrientation1, zeroAngVel)
assertVectorsAlmostEqual(self, AeroParameters.getNormalAeroForceDirection(state1, self.currentConditions), Vector(0, -1, 0))
state2 = RigidBodyState(zeroPos, self.dummyVelocity1, self.dummyOrientation2, zeroAngVel)
assertVectorsAlmostEqual(self, AeroParameters.getNormalAeroForceDirection(state2, self.currentConditions), Vector(0, 1, 0))
state3 = RigidBodyState(zeroPos, self.dummyVelocity1, self.dummyOrientation3, zeroAngVel)
assertVectorsAlmostEqual(self, AeroParameters.getNormalAeroForceDirection(state3, self.currentConditions), Vector(1, 0, 0))
state4 = RigidBodyState(zeroPos, self.dummyVelocity1, self.dummyOrientation4, zeroAngVel)
assertVectorsAlmostEqual(self, AeroParameters.getNormalAeroForceDirection(state4, self.currentConditions), Vector(1, 0, 0))
state5 = RigidBodyState(zeroPos, self.dummyVelocity1, self.dummyOrientation5, zeroAngVel)
assertVectorsAlmostEqual(self, AeroParameters.getNormalAeroForceDirection(state5, self.currentConditions), Vector(0.707, -0.707, 0),3)
assertVectorsAlmostEqual(self, AeroParameters.getNormalAeroForceDirection(self.rocketState8, self.currentConditions), Vector(-0.99999, 0.0022736, 0),3)
# Prep rocket by calling getLocalFrameAirVel first to cache AOA result, then get cached result from getTotalAOA
def testLocalFrameAirVelNormalForceDir(vel, orientation, expectedResult, precision=7):
state = RigidBodyState(Vector(0,0,0), vel, orientation, AngularVelocity(0,0,0))
assertVectorsAlmostEqual(self, AeroParameters.getNormalAeroForceDirection(state, self.currentConditions), expectedResult, precision)
testLocalFrameAirVelNormalForceDir(self.dummyVelocity1, self.dummyOrientation1, Vector(0, -1, 0))
testLocalFrameAirVelNormalForceDir(self.dummyVelocity1, self.dummyOrientation2, Vector(0, 1, 0))
testLocalFrameAirVelNormalForceDir(self.dummyVelocity1, self.dummyOrientation3, Vector(1, 0, 0))
testLocalFrameAirVelNormalForceDir(self.dummyVelocity1, self.dummyOrientation4, Vector(1, 0, 0))
testLocalFrameAirVelNormalForceDir(self.dummyVelocity1, self.dummyOrientation5, Vector(0.707, -0.707, 0), 3)
testLocalFrameAirVelNormalForceDir(self.rocketState8.velocity, self.rocketState8.orientation, Vector(-0.99999, 0.0022736, 0),3)
def testLocalFrameAirVelNormalForceDir(vel, orientation, expectedResult, precision=7):
state = RigidBodyState(Vector(0,0,0), vel, orientation, AngularVelocity(0,0,0))
assertVectorsAlmostEqual(self, AeroParameters.getNormalAeroForceDirection(state, self.currentConditions), expectedResult, precision)
