def getAppliedForce(self, rocketState, time, environment, CG):
Aref = self.rocket.Aref
Mach = AeroParameters.getMachNumber(rocketState, environment)
# Normal Force --------------------------------------------------------------------------------
# TODO: Account for rate of pitch/yaw rotation in AOA calculation? Or do separate Pitch/Yaw damping moments?
AOA = AeroParameters.getTotalAOA(rocketState, environment)
normalForceCoefficient = AeroFunctions.Barrowman_GetCN(
AOA, Aref, 0, self.baseArea)
# Drag Force ---------------------------------------------------------------------------------------------
#### Skin Friction ####
skinFrictionDragCoefficient, rollDampingMoment = AeroFunctions.getCylindricalSkinFrictionDragCoefficientAndRollDampingMoment(rocketState, environment, self.length, Mach, \
self.surfaceRoughness, self.wettedArea, Aref, self.rocket.finenessRatio, self.rocket.fullyTurbulentBL)
#### Pressure ####
pressureDragCoefficient = self._getCd_Pressure(Mach)
totalDragCoefficient = pressureDragCoefficient + skinFrictionDragCoefficient
# Damping moments --------------------------------------------------------------------------------------
# Roll damping due to skin friction
dampingMoments = rollDampingMoment
# Combine forces and return total -------------------------------------------------------------------------------------
return AeroFunctions.forceFromCdCN(rocketState,
environment,
totalDragCoefficient,
normalForceCoefficient,
self.CPLocation,
Aref,
moment=dampingMoments)
def getAppliedForce(self, rocketState, time, environment, CG):
Aref = self.rocket.Aref
# Normal Force ----------------------------------------------------------------------------------------
AOA = AeroParameters.getTotalAOA(rocketState, environment)
# Niskanen Eqn 3.26 - originally from Galejs
normalForceCoefficient = 1.1 * (math.sin(AOA))**2
normalForceCoefficient *= self.planformArea / Aref
# Drag -----------------------------------------------------------------------------------------------
# Skin Friction
Mach = AeroParameters.getMachNumber(rocketState, environment)
skinFrictionDragCoefficient, rollDampingMoment = AeroFunctions.getCylindricalSkinFrictionDragCoefficientAndRollDampingMoment(rocketState, environment, self.length, Mach, self.surfaceRoughness, \
self.wettedArea, Aref, self.rocket.finenessRatio, self.rocket.fullyTurbulentBL)
#There is no pressure drag associated with bodytubes - skin friction drag is total drag
# Damping moments --------------------------------------------------------------------------------------
dampingMoments = self._computeLongitudinalDampingMoments(rocketState, environment, CG)
# Roll damping due to skin friction
dampingMoments += rollDampingMoment
# Compute & dimensionalize total-------------------------------------------------------------------------
return AeroFunctions.forceFromCdCN(rocketState, environment, skinFrictionDragCoefficient, normalForceCoefficient, self.CPLocation, Aref, moment=dampingMoments)
def getAppliedForce(self, rocketState, time, environment,
CG) -> ForceMomentSystem:
Mach = AeroParameters.getMachNumber(rocketState, environment)
Aref = self.rocket.Aref
#### Normal Force ####
AOA = AeroParameters.getTotalAOA(rocketState, environment)
CN = AeroFunctions.Barrowman_GetCN(AOA, Aref, self.topArea,
self.bottomArea)
#### Pressure Drag ####
if self.startDiameter > self.endDiameter:
# Pressure base drag
Cd_base = AeroFunctions.getBaseDragCoefficient(Mach)
Cd_pressure = Cd_base * self.CdAdjustmentFactor
else:
# Pressure drag calculated like a nose cone
if Mach < 1:
# Niskanen pg. 48 eq. 3.87 - Power law interpolation
Cd_pressure = self.SubsonicCdPolyCoeffs[
0] * Mach**self.SubsonicCdPolyCoeffs[1]
elif Mach > 1 and Mach < 1.3:
# Interpolate in transonic region - derived from Niskanen Appendix B, Eqns B.3 - B.6
Cd_pressure = self.TransonicCdPolyCoeffs[0] + self.TransonicCdPolyCoeffs[1]*Mach + \
self.TransonicCdPolyCoeffs[2]*Mach**2 + self.TransonicCdPolyCoeffs[3]*Mach**3
else:
Cd_pressure = getSupersonicPressureDragCoeff_Hoerner(
self.coneHalfAngle, Mach)
# Make reference are the rocket's, not this objects
Cd_pressure *= self.frontalArea / Aref
#### Skin Friction Drag ####
if self.wettedArea == 0:
skinFrictionDragCoefficient = 0
rollDampingMoment = Vector(0, 0, 0)
else:
skinFrictionDragCoefficient, rollDampingMoment = AeroFunctions.getCylindricalSkinFrictionDragCoefficientAndRollDampingMoment(rocketState, environment, \
self.length, Mach, self.surfaceRoughness, self.wettedArea, Aref, self.rocket.finenessRatio, self.rocket.fullyTurbulentBL)
#### Total Drag ####
Cd = Cd_pressure + skinFrictionDragCoefficient
#### Assemble & return final force object ####
return AeroFunctions.forceFromCdCN(rocketState,
environment,
Cd,
CN,
self.CPLocation,
Aref,
moment=rollDampingMoment)
def getAppliedForce(self, rocketState, time, environment,
CG) -> ForceMomentSystem:
Mach = AeroParameters.getMachNumber(rocketState, environment)
Aref = self.rocket.Aref
#### Normal Force ####
AOA = AeroParameters.getTotalAOA(rocketState, environment)
CN = AeroFunctions.Barrowman_GetCN(AOA, Aref, self.topArea,
self.bottomArea)
#### Pressure Drag ####
Cd_base = AeroFunctions.getBaseDragCoefficient(Mach)
Cd_pressure = Cd_base * self.CdAdjustmentFactor
Cd_pressure *= self.frontalArea / self.rocket.Aref
noEngine = (self.stage.engineShutOffTime == None)
if noEngine or time > self.stage.engineShutOffTime:
# Add base drag if engine is off
Cd_pressure += Cd_base * self.bottomArea / Aref
#### Skin Friction Drag ####
if self.wettedArea == 0:
skinFrictionDragCoefficient = 0
rollDampingMoment = Vector(0, 0, 0)
else:
skinFrictionDragCoefficient, rollDampingMoment = AeroFunctions.getCylindricalSkinFrictionDragCoefficientAndRollDampingMoment(rocketState, environment, \
self.length, Mach, self.surfaceRoughness, self.wettedArea, Aref, self.rocket.finenessRatio, self.rocket.fullyTurbulentBL)
#### Total Drag ####
Cd = Cd_pressure + skinFrictionDragCoefficient
#### Assemble & return final force object ####
return AeroFunctions.forceFromCdCN(rocketState,
environment,
Cd,
CN,
self.CPLocation,
Aref,
moment=rollDampingMoment)
def _getAppliedForce(self, time, state):
''' Get the total force currently being experienced by the rocket, used by self.rigidBody to calculate the rocket's acceleration '''
### Precomputations and Logging ###
environment = self._getEnvironmentalConditions(time, state) # Get and log current air/wind properties
rocketInertia = self.getInertia(time, state) # Get and log current rocket inertia
if self.derivativeEvaluationLog is not None:
self.derivativeEvaluationLog.newLogRow(time)
self.derivativeEvaluationLog.logValue("Position(m)", state.position)
self.derivativeEvaluationLog.logValue("Velocity(m/s)", state.velocity)
### Component Forces ###
if not self.isUnderChute:
# Precompute and log
Mach = AeroParameters.getMachNumber(state, environment)
unitRe = AeroParameters.getReynoldsNumber(state, environment, 1.0)
AOA = AeroParameters.getTotalAOA(state, environment)
rollAngle = AeroParameters.getRollAngle(state, environment)
if self.derivativeEvaluationLog is not None:
self.derivativeEvaluationLog.logValue("Mach", Mach)
self.derivativeEvaluationLog.logValue("UnitRe", unitRe)
self.derivativeEvaluationLog.logValue("AOA(deg)", math.degrees(AOA))
self.derivativeEvaluationLog.logValue("RollAngle(deg)", rollAngle)
self.derivativeEvaluationLog.logValue("OrientationQuaternion", state.orientation)
self.derivativeEvaluationLog.logValue("AngularVelocity(rad/s)", state.angularVelocity)
# This function will be the inherited function CompositeObject.getAppliedForce
componentForces = self.getAppliedForce(state, time, environment, rocketInertia.CG)
else:
# When under chute, neglect forces from other components
componentForces = self.recoverySystem.getAppliedForce(state, time, environment, Vector(0,0,-1))
# Log the recovery system's applied force (Normally handled in CompositeObject.getAppliedForce)
if hasattr(self.recoverySystem, "forcesLog"):
self.recoverySystem.forcesLog.append(componentForces.force)
self.recoverySystem.momentsLog.append(componentForces.moment)
# Move Force-Moment system to rocket CG
componentForces = componentForces.getAt(rocketInertia.CG)
### Gravity ###
gravityForce = self.environment.getGravityForce(rocketInertia, state)
totalForce = componentForces + gravityForce
### Launch Rail ###
totalForce = self.environment.applyLaunchTowerForce(state, time, totalForce)
if self.derivativeEvaluationLog is not None:
self.derivativeEvaluationLog.logValue("Wind(m/s)", environment.Wind)
self.derivativeEvaluationLog.logValue("AirDensity(kg/m^3)", environment.Density)
self.derivativeEvaluationLog.logValue("CG(m)", rocketInertia.CG)
self.derivativeEvaluationLog.logValue("MOI(kg*m^2)", rocketInertia.MOI)
self.derivativeEvaluationLog.logValue("Mass(kg)", rocketInertia.mass)
CPZ = AeroFunctions._getCPZ(componentForces)
self.derivativeEvaluationLog.logValue("CPZ(m)", CPZ)
self.derivativeEvaluationLog.logValue("AeroF(N)", componentForces.force)
self.derivativeEvaluationLog.logValue("AeroM(Nm)", componentForces.moment)
self.derivativeEvaluationLog.logValue("GravityF(N)", gravityForce.force)
self.derivativeEvaluationLog.logValue("TotalF(N)", totalForce.force)
return totalForce
def test_getMachNumber(self):
environment = self.environment.getAirProperties(Vector(0,0,0))
# Assumes gamma=1.4, R=287
self.assertAlmostEqual(AeroParameters.getMachNumber(self.rocketState1, environment), 0.587781235)
def _barrowmanAeroFunc(self,
rocketState,
time,
environment,
precomputedData,
CG=Vector(0, 0, 0),
finDeflectionAngle=None):
'''
Precomputed Data is a named tuple (PreComputedFinAeroData) which contains data/results from the parts of the fin aerodynamics calculation
that are common to all fins in a FinSet (drag calculations mostly). These calculations are performed at the FinSet level.
Only the parts of the Fin Aero Computation that change from fin to fin (normal force mostly, since different fins can have different angles of attack) are computed here
'''
Mach = AeroParameters.getMachNumber(rocketState, environment)
dynamicPressure = AeroParameters.getDynamicPressure(
rocketState, environment)
if finDeflectionAngle == None:
finDeflectionAngle = self.finAngle # Adjusted by parent finset during each timestep, when the FinSet is controlled
# Unpack precomputedData
airVelRelativeToFin, CPXPos, totalDragCoefficient = precomputedData
#### Compute normal force-----------------------------------------------------------------------------------------------------------------
# Find fin normal vector after fin deflection
finDeflectionRotation = Quaternion(
axisOfRotation=self.spanwiseDirection,
angle=radians(finDeflectionAngle))
finNormal = finDeflectionRotation.rotate(self.undeflectedFinNormal)
# Get the tangential velocity component vector, per unit radial distance from the rocket centerline
rollAngVel = AngularVelocity(0, 0, rocketState.angularVelocity.Z)
unitSpanTangentialAirVelocity = rollAngVel.crossProduct(
self.spanwiseDirection) * (-1)
def subsonicNormalForce(Mach): # Subsonic linear method
tempBeta = AeroParameters.getBeta(Mach)
CnAlpha = getFinCnAlpha_Subsonic_Barrowman(self.span,
self.planformArea,
tempBeta,
self.midChordSweep)
return getSubsonicFinNormalForce(airVelRelativeToFin,
unitSpanTangentialAirVelocity,
finNormal, self.spanwiseDirection,
self.CPSpanWisePosition.length(),
CnAlpha, self)
def supersonicNormalForce(Mach): # Supersonic Busemann method
gamma = AeroFunctions.getGamma()
tempBeta = AeroParameters.getBeta(Mach)
K1, K2, K3, Kstar = getBusemannCoefficients(Mach, tempBeta, gamma)
# Mach Cone coords
machAngle = asin(1 / Mach)
machCone_negZPerRadius = 1 / tan(machAngle)
machConeEdgeZPos = []
outerRadius = self.spanSliceRadii[-1]
for i in range(len(self.spanSliceRadii)):
machConeAtCurrentRadius = (
outerRadius - self.spanSliceRadii[i]
) * machCone_negZPerRadius + self.tipPosition
machConeEdgeZPos.append(machConeAtCurrentRadius)
return getSupersonicFinNormalForce(
airVelRelativeToFin, unitSpanTangentialAirVelocity, finNormal,
machConeEdgeZPos, self.spanwiseDirection,
self.CPSpanWisePosition.length(), K1, K2, K3, Kstar, self)
if Mach <= 0.8:
normalForceMagnitude, finMoment = subsonicNormalForce(Mach)
elif Mach < 1.4:
# Interpolate in transonic region
# TODO: Do this with less function evaluations? Perhaps precompute AOA and Mach combinations and simply interpolate? Lazy precompute? Cython?
x1, x2 = 0.8, 1.4 # Start, end pts of interpolated region
dx = 0.001
# Find normal force and derivative at start of interpolation interval
f_x1, m_x1 = subsonicNormalForce(x1)
f_x12, m_x12 = subsonicNormalForce(x1 + dx)
# Find normal force and derivative at end of interpolation interval
f_x2, m_x2 = supersonicNormalForce(x2)
f_x22, m_x22 = supersonicNormalForce(x2 + dx)
normalForceMagnitude = Interpolation.cubicInterp(
Mach, x1, x2, f_x1, f_x2, f_x12, f_x22, dx)
finMoment = Interpolation.cubicInterp(Mach, x1, x2, m_x1, m_x2,
m_x12, m_x22, dx)
else:
normalForceMagnitude, finMoment = supersonicNormalForce(Mach)
# Complete redimensionalization of normal force coefficients by multiplying by dynamic pressure
# Direct the normal force along the fin's normal direction
normalForce = normalForceMagnitude * dynamicPressure * finNormal
finMoment *= dynamicPressure
#### Get axial force-----------------------------------------------------------------------------------------------------------------------
avgAOA = getFinSliceAngleOfAttack(
self.spanSliceRadii[round(len(self.spanSliceAreas) / 2)],
airVelRelativeToFin, unitSpanTangentialAirVelocity, finNormal,
self.spanwiseDirection,
self.stallAngle) # Approximate average fin AOA
totalAxialForceCoefficient = AeroFunctions.getDragToAxialForceFactor(
avgAOA) * totalDragCoefficient
axialForceMagnitude = totalAxialForceCoefficient * self.rocket.Aref * dynamicPressure
axialForceDirection = self.spanwiseDirection.crossProduct(finNormal)
axialForce = axialForceDirection * axialForceMagnitude
#### Get CP Location ----------------------------------------------------------------------------------------------------------------------
CPChordWisePosition = self.position - Vector(
0, 0, CPXPos
) # Ignoring the change in CP position due to fin deflection for now
globalCP = self.CPSpanWisePosition + CPChordWisePosition
#### Assemble total force moment system objects--------------------------------------------------------------------------------------------
totalForce = normalForce + axialForce
return ForceMomentSystem(totalForce,
globalCP,
moment=Vector(0, 0, finMoment)), globalCP
def _getPreComputedFinAeroData(self, rocketState, environment, CG):
#General Info ---------------------------------------------------------------------------------------------------------------------
Aref = self.rocket.Aref
Mach = AeroParameters.getMachNumber(rocketState, environment)
dynamicPressure = AeroParameters.getDynamicPressure(
rocketState, environment)
# Skin Friction Drag -------------------------------------------------------------------------------------------------------------
skinFrictionCoefficient = AeroFunctions.getSkinFrictionCoefficient(
rocketState, environment, self.MACLength, Mach,
self.surfaceRoughness, self.rocket.fullyTurbulentBL)
# Adjust to the rocket reference area (skinFrictionCoefficient is based on wetted area)
skinFrictionDragCoefficient = skinFrictionCoefficient * (
self.wettedArea / Aref)
# Correct for additional surface area due to fin thickness - Niskanen Eqn 3.85
skinFrictionDragCoefficient *= (1 +
2 * self.thickness / self.MACLength)
# Pressure Drag ------------------------------------------------------------------------------------------------------------------
# Leading edge drag coefficient
if self.leadingEdgeShape == "Round":
leadingEdgeCd = AeroFunctions.getCylinderCrossFlowCd_ZeroBaseDrag(
Mach)
LEthickness = self.leadingEdgeRadius * 2
elif self.leadingEdgeShape == "Blunt":
leadingEdgeCd = AeroFunctions.getBluntBodyCd_ZeroBaseDrag(Mach)
LEthickness = self.leadingEdgeThickness
# Adjust for leading edge angle and convert reference area to rocket reference area - Barrowman Eqn 4-22
leadingEdgeCdAdjustmentFactor = LEthickness * self.span * cos(
self.sweepAngle)**2 / Aref
leadingEdgeCd *= leadingEdgeCdAdjustmentFactor
# Trailing edge drag coefficient - simpler method from Niskanen section 3.4.4. Corrected to use only the trailing edge area, not the full fin frontal area
# more intricate method available in Barrowman
baseDragCd = AeroFunctions.getBaseDragCoefficient(Mach)
if self.trailingEdgeShape == "Tapered":
TEthickness = 0 # Zero base drag
elif self.trailingEdgeShape == "Round":
TEthickness = self.trailingEdgeRadius # 0.5 base drag
elif self.trailingEdgeShape == "Blunt":
TEthickness = self.trailingEdgeThickness # Full base drag
# Convert to standard rocket reference Area
trailingEdgeCd = baseDragCd * self.span * TEthickness / Aref
# Thickness / Wave Drag
#TODO: This section doesn't seem to be working quite right
if Mach <= 1:
# Thickness drag, subsonic
thicknessDrag = 4*skinFrictionCoefficient*((self.thickness/self.rootChord)*cos(self.midChordSweep) + \
(30 * (self.thickness/self.rootChord)**4 * cos(self.midChordSweep)**2) / \
(self.subsonicFinThicknessK - Mach**2 * cos(self.midChordSweep)**2)**(3/2))
else:
# Supersonic wave drag
# Using simplistic method from Hoerner - assumes diamond profile (pg 17-12, Eqn 29)
# TODO: Implement method from Barrowman's FIN program
thicknessDrag = 2.3 * self.aspectRatio * (self.thickness /
self.MACLength)**2
thicknessDrag *= self.planformArea / Aref
pressureDragCoefficient = leadingEdgeCd + trailingEdgeCd + thicknessDrag
# Total Drag --------------------------------------------------------------------------------------------------------------------
totalDragCoefficient = pressureDragCoefficient + skinFrictionDragCoefficient
localFrameRocketVelocity = AeroParameters.getLocalFrameAirVel(
rocketState, environment)
axialPositionRelCG = self.position - CG
finVelocityDueToRocketPitchYaw = rocketState.angularVelocity.crossProduct(
axialPositionRelCG)
airVelRelativeToFin = localFrameRocketVelocity - finVelocityDueToRocketPitchYaw # The negative puts it in the wind frame
CPXPos = self._getCPXPos(Mach)
#### Transfer info to fins ####
return PreComputedFinAeroData(airVelRelativeToFin, CPXPos,
totalDragCoefficient)
