def update_forces(segment, state):
# unpack
conditions = state.conditions
# unpack forces
wind_lift_force_vector = conditions.frames.wind.lift_force_vector
wind_drag_force_vector = conditions.frames.wind.drag_force_vector
body_thrust_force_vector = conditions.frames.body.thrust_force_vector
inertial_gravity_force_vector = conditions.frames.inertial.gravity_force_vector
# unpack transformation matrices
T_body2inertial = conditions.frames.body.transform_to_inertial
T_wind2inertial = conditions.frames.wind.transform_to_inertial
# to inertial frame
L = orientation_product(T_wind2inertial, wind_lift_force_vector)
D = orientation_product(T_wind2inertial, wind_drag_force_vector)
T = orientation_product(T_body2inertial, body_thrust_force_vector)
W = inertial_gravity_force_vector
# sum of the forces
F = L + D + T + W
# like a boss
# pack
conditions.frames.inertial.total_force_vector[:, :] = F[:, :]
return
def update_forces(segment,state):
# unpack
conditions = state.conditions
# unpack forces
wind_lift_force_vector = conditions.frames.wind.lift_force_vector
wind_drag_force_vector = conditions.frames.wind.drag_force_vector
body_thrust_force_vector = conditions.frames.body.thrust_force_vector
inertial_gravity_force_vector = conditions.frames.inertial.gravity_force_vector
# unpack transformation matrices
T_body2inertial = conditions.frames.body.transform_to_inertial
T_wind2inertial = conditions.frames.wind.transform_to_inertial
# to inertial frame
L = orientation_product(T_wind2inertial,wind_lift_force_vector)
D = orientation_product(T_wind2inertial,wind_drag_force_vector)
T = orientation_product(T_body2inertial,body_thrust_force_vector)
W = inertial_gravity_force_vector
# sum of the forces
F = L + D + T + W
# like a boss
# pack
conditions.frames.inertial.total_force_vector[:,:] = F[:,:]
return
def update_forces(segment,state):
""" Summation of forces: lift, drag, thrust, weight. Future versions will include new definitions of dreams, FAA, money, and reality.
Assumptions:
You only have these 4 forces applied to the vehicle
Inputs:
state.conditions:
frames.wind.lift_force_vector [newtons]
frames.wind.drag_force_vector [newtons]
frames.inertial.gravity_force_vector [newtons]
frames.body.thrust_force_vector [newtons]
frames.body.transform_to_inertial [newtons]
frames.wind.transform_to_inertial [newtons]
Outputs:
state.conditions:
frames.inertial.total_force_vector [newtons]
Properties Used:
N/A
"""
# unpack
conditions = state.conditions
# unpack forces
wind_lift_force_vector = conditions.frames.wind.lift_force_vector
wind_drag_force_vector = conditions.frames.wind.drag_force_vector
body_thrust_force_vector = conditions.frames.body.thrust_force_vector
inertial_gravity_force_vector = conditions.frames.inertial.gravity_force_vector
# unpack transformation matrices
T_body2inertial = conditions.frames.body.transform_to_inertial
T_wind2inertial = conditions.frames.wind.transform_to_inertial
# to inertial frame
L = orientation_product(T_wind2inertial,wind_lift_force_vector)
D = orientation_product(T_wind2inertial,wind_drag_force_vector)
T = orientation_product(T_body2inertial,body_thrust_force_vector)
W = inertial_gravity_force_vector
# sum of the forces
F = L + D + T + W
# like a boss
# pack
conditions.frames.inertial.total_force_vector[:,:] = F[:,:]
return
def update_forces(segment):
""" Summation of forces: lift, drag, thrust, weight. Future versions will include new definitions of dreams, FAA, money, and reality.
Assumptions:
You only have these 4 forces applied to the vehicle
Inputs:
segment.state.conditions:
frames.wind.lift_force_vector [newtons]
frames.wind.drag_force_vector [newtons]
frames.inertial.gravity_force_vector [newtons]
frames.body.thrust_force_vector [newtons]
frames.body.transform_to_inertial [newtons]
frames.wind.transform_to_inertial [newtons]
Outputs:
segment.state.conditions:
frames.inertial.total_force_vector [newtons]
Properties Used:
N/A
"""
# unpack
conditions = segment.state.conditions
# unpack forces
wind_lift_force_vector = conditions.frames.wind.lift_force_vector
wind_drag_force_vector = conditions.frames.wind.drag_force_vector
body_thrust_force_vector = conditions.frames.body.thrust_force_vector
inertial_gravity_force_vector = conditions.frames.inertial.gravity_force_vector
# unpack transformation matrices
T_body2inertial = conditions.frames.body.transform_to_inertial
T_wind2inertial = conditions.frames.wind.transform_to_inertial
# to inertial frame
L = orientation_product(T_wind2inertial, wind_lift_force_vector)
D = orientation_product(T_wind2inertial, wind_drag_force_vector)
T = orientation_product(T_body2inertial, body_thrust_force_vector)
W = inertial_gravity_force_vector
# sum of the forces
F = L + D + T + W
# like a boss
# pack
conditions.frames.inertial.total_force_vector[:, :] = F[:, :]
return
def compute_ground_forces(segment):
""" Compute the rolling friction on the aircraft
Assumptions:
Does a force balance to calculate the load on the wheels using only lift. Uses only a single friction coefficient.
Source:
N/A
Inputs:
conditions:
frames.inertial.gravity_force_vector [meters/second^2]
ground.friction_coefficient [unitless]
frames.wind.lift_force_vector [newtons]
Outputs:
conditions.frames.inertial.ground_force_vector [newtons]
Properties Used:
N/A
"""
# unpack
conditions = segment.state.conditions
W = conditions.frames.inertial.gravity_force_vector[:, 2, None]
friction_coeff = conditions.ground.friction_coefficient
wind_lift_force_vector = conditions.frames.wind.lift_force_vector
#transformation matrix to get lift in inertial frame
T_wind2inertial = conditions.frames.wind.transform_to_inertial
# to inertial frame
L = orientation_product(T_wind2inertial, wind_lift_force_vector)[:, 2,
None]
#compute friction force
N = -(W + L)
Ff = N * friction_coeff
#pack results. Friction acts along x-direction
conditions.frames.inertial.ground_force_vector[:, 2] = N[:, 0]
conditions.frames.inertial.ground_force_vector[:, 0] = Ff[:, 0]
def compute_ground_forces(segment):
""" Compute the rolling friction on the aircraft
Assumptions:
Does a force balance to calculate the load on the wheels using only lift. Uses only a single friction coefficient.
Source:
N/A
Inputs:
conditions:
frames.inertial.gravity_force_vector [meters/second^2]
ground.friction_coefficient [unitless]
frames.wind.lift_force_vector [newtons]
Outputs:
conditions.frames.inertial.ground_force_vector [newtons]
Properties Used:
N/A
"""
# unpack
conditions = segment.state.conditions
W = conditions.frames.inertial.gravity_force_vector[:,2,None]
friction_coeff = conditions.ground.friction_coefficient
wind_lift_force_vector = conditions.frames.wind.lift_force_vector
#transformation matrix to get lift in inertial frame
T_wind2inertial = conditions.frames.wind.transform_to_inertial
# to inertial frame
L = orientation_product(T_wind2inertial,wind_lift_force_vector)[:,2,None]
#compute friction force
N = -(W + L)
Ff = N * friction_coeff
#pack results. Friction acts along x-direction
conditions.frames.inertial.ground_force_vector[:,2] = N[:,0]
conditions.frames.inertial.ground_force_vector[:,0] = Ff[:,0]
def compute_ground_forces(segment,state):
""" Compute the rolling friction on the aircraft """
# unpack
conditions = state.conditions
W = conditions.frames.inertial.gravity_force_vector[:,2,None]
friction_coeff = conditions.ground.friction_coefficient
wind_lift_force_vector = conditions.frames.wind.lift_force_vector
#transformation matrix to get lift in inertial frame
T_wind2inertial = conditions.frames.wind.transform_to_inertial
# to inertial frame
L = orientation_product(T_wind2inertial,wind_lift_force_vector)[:,2,None]
#compute friction force
N = -(W + L)
Ff = N * friction_coeff
#pack results. Friction acts along x-direction
conditions.frames.inertial.ground_force_vector[:,2] = N[:,0]
conditions.frames.inertial.ground_force_vector[:,0] = Ff[:,0]
def compute_ground_forces(segment, state):
""" Compute the rolling friction on the aircraft """
# unpack
conditions = state.conditions
W = conditions.frames.inertial.gravity_force_vector[:, 2, None]
friction_coeff = conditions.ground.friction_coefficient
wind_lift_force_vector = conditions.frames.wind.lift_force_vector
#transformation matrix to get lift in inertial frame
T_wind2inertial = conditions.frames.wind.transform_to_inertial
# to inertial frame
L = orientation_product(T_wind2inertial, wind_lift_force_vector)[:, 2,
None]
#compute friction force
N = -(W + L)
Ff = N * friction_coeff
#pack results. Friction acts along x-direction
conditions.frames.inertial.ground_force_vector[:, 2] = N[:, 0]
conditions.frames.inertial.ground_force_vector[:, 0] = Ff[:, 0]
def spin(self,conditions):
"""Analyzes a propeller given geometry and operating conditions.
Assumptions:
per source
Source:
Drela, M. "Qprop Formulation", MIT AeroAstro, June 2006
http://web.mit.edu/drela/Public/web/qprop/qprop_theory.pdf
Leishman, Gordon J. Principles of helicopter aerodynamics
Cambridge university press, 2006.
Inputs:
self.inputs.omega [radian/s]
conditions.freestream.
density [kg/m^3]
dynamic_viscosity [kg/(m-s)]
speed_of_sound [m/s]
temperature [K]
conditions.frames.
body.transform_to_inertial (rotation matrix)
inertial.velocity_vector [m/s]
conditions.propulsion.
throttle [-]
Outputs:
conditions.propulsion.outputs.
number_radial_stations [-]
number_azimuthal_stations [-]
disc_radial_distribution [m]
thrust_angle [rad]
speed_of_sound [m/s]
density [kg/m-3]
velocity [m/s]
disc_tangential_induced_velocity [m/s]
disc_axial_induced_velocity [m/s]
disc_tangential_velocity [m/s]
disc_axial_velocity [m/s]
drag_coefficient [-]
lift_coefficient [-]
omega [rad/s]
disc_circulation [-]
blade_dQ_dR [N/m]
blade_dT_dr [N]
blade_thrust_distribution [N]
disc_thrust_distribution [N]
thrust_per_blade [N]
thrust_coefficient [-]
azimuthal_distribution [rad]
disc_azimuthal_distribution [rad]
blade_dQ_dR [N]
blade_dQ_dr [Nm]
blade_torque_distribution [Nm]
disc_torque_distribution [Nm]
torque_per_blade [Nm]
torque_coefficient [-]
power [W]
power_coefficient [-]
Properties Used:
self.
number_of_blades [-]
tip_radius [m]
hub_radius [m]
twist_distribution [radians]
chord_distribution [m]
mid_chord_alignment [m]
thrust_angle [radians]
"""
#Unpack
B = self.number_of_blades
R = self.tip_radius
Rh = self.hub_radius
beta_0 = self.twist_distribution
c = self.chord_distribution
chi = self.radius_distribution
omega = self.inputs.omega
a_geo = self.airfoil_geometry
a_loc = self.airfoil_polar_stations
cl_sur = self.airfoil_cl_surrogates
cd_sur = self.airfoil_cd_surrogates
tc = self.thickness_to_chord
ua = self.induced_hover_velocity
VTOL = self.VTOL_flag
rho = conditions.freestream.density[:,0,None]
mu = conditions.freestream.dynamic_viscosity[:,0,None]
Vv = conditions.frames.inertial.velocity_vector
a = conditions.freestream.speed_of_sound[:,0,None]
T = conditions.freestream.temperature[:,0,None]
pitch_c = self.pitch_command
theta = self.thrust_angle
Na = self.number_azimuthal_stations
BB = B*B
BBB = BB*B
nonuniform_freestream = self.nonuniform_freestream
rotation = self.rotation
# calculate total blade pitch
total_blade_pitch = beta_0 + pitch_c
# Velocity in the Body frame
T_body2inertial = conditions.frames.body.transform_to_inertial
T_inertial2body = orientation_transpose(T_body2inertial)
V_body = orientation_product(T_inertial2body,Vv)
body2thrust = np.array([[np.cos(theta), 0., np.sin(theta)],[0., 1., 0.], [-np.sin(theta), 0., np.cos(theta)]])
T_body2thrust = orientation_transpose(np.ones_like(T_body2inertial[:])*body2thrust)
V_thrust = orientation_product(T_body2thrust,V_body)
if VTOL:
V = V_thrust[:,0,None] + ua
else:
V = V_thrust[:,0,None]
ut = np.zeros_like(V)
#Things that don't change with iteration
Nr = len(c) # Number of stations radially
ctrl_pts = len(Vv)
# set up non dimensional radial distribution
chi = self.radius_distribution/R
V = V_thrust[:,0,None]
omega = np.abs(omega)
r = chi*R # Radial coordinate
omegar = np.outer(omega,r)
pi = np.pi
pi2 = pi*pi
n = omega/(2.*pi) # Cycles per second
nu = mu/rho
deltar = (r[1]-r[0])
deltachi = (chi[1]-chi[0])
rho_0 = rho
# azimuth distribution
psi = np.linspace(0,2*pi,Na+1)[:-1]
psi_2d = np.tile(np.atleast_2d(psi).T,(1,Nr))
psi_2d = np.repeat(psi_2d[np.newaxis, :, :], ctrl_pts, axis=0)
# 2D radial distribution non dimensionalized
chi_2d = np.tile(chi ,(Na,1))
chi_2d = np.repeat(chi_2d[ np.newaxis,:, :], ctrl_pts, axis=0)
r_dim_2d = np.tile(r ,(Na,1))
r_dim_2d = np.repeat(r_dim_2d[ np.newaxis,:, :], ctrl_pts, axis=0)
# Setup a Newton iteration
diff = 1.
ii = 0
tol = 1e-6 # Convergence tolerance
use_2d_analysis = False
if theta !=0:
# thrust angle creates disturbances in radial and tangential velocities
use_2d_analysis = True
# component of freestream in the propeller plane
Vz = V_thrust[:,2,None,None]
Vz = np.repeat(Vz, Na,axis=1)
Vz = np.repeat(Vz, Nr,axis=2)
if rotation == None:
print("Propeller rotation not specified. Set to 1 (clockwise when viewed from behind).")
rotation = 1
# compute resulting radial and tangential velocities in propeller frame
ut = ( Vz*np.cos(psi_2d) ) * rotation
ur = (-Vz*np.sin(psi_2d) )
ua = np.zeros_like(ut)
if nonuniform_freestream:
use_2d_analysis = True
# account for upstream influences
ua = self.axial_velocities_2d
ut = self.tangential_velocities_2d
ur = self.radial_velocities_2d
if use_2d_analysis:
# make everything 2D with shape (ctrl_pts,Na,Nr)
size = (ctrl_pts,Na,Nr)
PSI = np.ones(size)
PSIold = np.zeros(size)
# 2-D freestream velocity and omega*r
V_2d = V_thrust[:,0,None,None]
V_2d = np.repeat(V_2d, Na,axis=1)
V_2d = np.repeat(V_2d, Nr,axis=2)
omegar = (np.repeat(np.outer(omega,r)[:,None,:], Na, axis=1))
# total velocities
Ua = V_2d + ua
# 2-D blade pitch and radial distributions
beta = np.tile(total_blade_pitch,(Na ,1))
beta = np.repeat(beta[np.newaxis,:, :], ctrl_pts, axis=0)
r = np.tile(r,(Na ,1))
r = np.repeat(r[np.newaxis,:, :], ctrl_pts, axis=0)
# 2-D atmospheric properties
a = np.tile(np.atleast_2d(a),(1,Nr))
a = np.repeat(a[:, np.newaxis, :], Na, axis=1)
nu = np.tile(np.atleast_2d(nu),(1,Nr))
nu = np.repeat(nu[:, np.newaxis, :], Na, axis=1)
rho = np.tile(np.atleast_2d(rho),(1,Nr))
rho = np.repeat(rho[:, np.newaxis, :], Na, axis=1)
T = np.tile(np.atleast_2d(T),(1,Nr))
T = np.repeat(T[:, np.newaxis, :], Na, axis=1)
else:
# uniform freestream
ua = np.zeros_like(V)
ut = np.zeros_like(V)
ur = np.zeros_like(V)
# total velocities
Ua = np.outer((V + ua),np.ones_like(r))
beta = total_blade_pitch
# Things that will change with iteration
size = (ctrl_pts,Nr)
PSI = np.ones(size)
PSIold = np.zeros(size)
# total velocities
Ut = omegar - ut
U = np.sqrt(Ua*Ua + Ut*Ut + ur*ur)
# Drela's Theory
while (diff>tol):
sin_psi = np.sin(PSI)
cos_psi = np.cos(PSI)
Wa = 0.5*Ua + 0.5*U*sin_psi
Wt = 0.5*Ut + 0.5*U*cos_psi
va = Wa - Ua
vt = Ut - Wt
alpha = beta - np.arctan2(Wa,Wt)
W = (Wa*Wa + Wt*Wt)**0.5
Ma = (W)/a # a is the speed of sound
lamdaw = r*Wa/(R*Wt)
# Limiter to keep from Nan-ing
lamdaw[lamdaw<0.] = 0.
f = (B/2.)*(1.-r/R)/lamdaw
f[f<0.] = 0.
piece = np.exp(-f)
arccos_piece = np.arccos(piece)
F = 2.*arccos_piece/pi # Prandtl's tip factor
Gamma = vt*(4.*pi*r/B)*F*(1.+(4.*lamdaw*R/(pi*B*r))*(4.*lamdaw*R/(pi*B*r)))**0.5
Re = (W*c)/nu
# Compute aerodynamic forces based on specified input airfoil or using a surrogate
Cl, Cdval = compute_aerodynamic_forces(a_loc, a_geo, cl_sur, cd_sur, ctrl_pts, Nr, Na, Re, Ma, alpha, tc, use_2d_analysis)
Rsquiggly = Gamma - 0.5*W*c*Cl
# An analytical derivative for dR_dpsi, this is derived by taking a derivative of the above equations
# This was solved symbolically in Matlab and exported
f_wt_2 = 4*Wt*Wt
f_wa_2 = 4*Wa*Wa
Ucospsi = U*cos_psi
Usinpsi = U*sin_psi
Utcospsi = Ut*cos_psi
Uasinpsi = Ua*sin_psi
UapUsinpsi = (Ua + Usinpsi)
utpUcospsi = (Ut + Ucospsi)
utpUcospsi2 = utpUcospsi*utpUcospsi
UapUsinpsi2 = UapUsinpsi*UapUsinpsi
dR_dpsi = ((4.*U*r*arccos_piece*sin_psi*((16.*UapUsinpsi2)/(BB*pi2*f_wt_2) + 1.)**(0.5))/B -
(pi*U*(Ua*cos_psi - Ut*sin_psi)*(beta - np.arctan((Wa+Wa)/(Wt+Wt))))/(2.*(f_wt_2 + f_wa_2)**(0.5))
+ (pi*U*(f_wt_2 +f_wa_2)**(0.5)*(U + Utcospsi + Uasinpsi))/(2.*(f_wa_2/(f_wt_2) + 1.)*utpUcospsi2)
- (4.*U*piece*((16.*UapUsinpsi2)/(BB*pi2*f_wt_2) + 1.)**(0.5)*(R - r)*(Ut/2. -
(Ucospsi)/2.)*(U + Utcospsi + Uasinpsi ))/(f_wa_2*(1. - np.exp(-(B*(Wt+Wt)*(R -
r))/(r*(Wa+Wa))))**(0.5)) + (128.*U*r*arccos_piece*(Wa+Wa)*(Ut/2. - (Ucospsi)/2.)*(U +
Utcospsi + Uasinpsi ))/(BBB*pi2*utpUcospsi*utpUcospsi2*((16.*f_wa_2)/(BB*pi2*f_wt_2) + 1.)**(0.5)))
dR_dpsi[np.isnan(dR_dpsi)] = 0.1
dpsi = -Rsquiggly/dR_dpsi
PSI = PSI + dpsi
diff = np.max(abs(PSIold-PSI))
PSIold = PSI
# omega = 0, do not run BEMT convergence loop
if all(omega[:,0]) == 0. :
break
# If its really not going to converge
if np.any(PSI>pi/2) and np.any(dpsi>0.0):
print("Propeller BEMT did not converge to a solution (Stall)")
break
ii+=1
if ii>10000:
print("Propeller BEMT did not converge to a solution (Iteration Limit)")
break
# More Cd scaling from Mach from AA241ab notes for turbulent skin friction
Tw_Tinf = 1. + 1.78*(Ma*Ma)
Tp_Tinf = 1. + 0.035*(Ma*Ma) + 0.45*(Tw_Tinf-1.)
Tp = (Tp_Tinf)*T
Rp_Rinf = (Tp_Tinf**2.5)*(Tp+110.4)/(T+110.4)
Cd = ((1/Tp_Tinf)*(1/Rp_Rinf)**0.2)*Cdval
epsilon = Cd/Cl
epsilon[epsilon==np.inf] = 10.
blade_T_distribution = rho*(Gamma*(Wt-epsilon*Wa))*deltar
blade_Q_distribution = rho*(Gamma*(Wa+epsilon*Wt)*r)*deltar
if use_2d_analysis:
blade_T_distribution_2d = blade_T_distribution
blade_Q_distribution_2d = blade_Q_distribution
blade_Gamma_2d = Gamma
# set 1d blade loadings to be the average:
blade_T_distribution = np.mean((blade_T_distribution_2d), axis = 1)
blade_Q_distribution = np.mean((blade_Q_distribution_2d), axis = 1)
Va_2d = Wa
Vt_2d = Wt
Va_avg = np.average(Wa, axis=1) # averaged around the azimuth
Vt_avg = np.average(Wt, axis=1) # averaged around the azimuth
Va_ind_2d = va
Vt_ind_2d = vt
Vt_ind_avg = np.average(vt, axis=1)
Va_ind_avg = np.average(va, axis=1)
else:
Va_2d = np.repeat(Wa.T[ : , np.newaxis , :], Na, axis=1).T
Vt_2d = np.repeat(Wt.T[ : , np.newaxis , :], Na, axis=1).T
blade_T_distribution_2d = np.repeat(blade_T_distribution.T[ np.newaxis,: , :], Na, axis=0).T
blade_Q_distribution_2d = np.repeat(blade_Q_distribution.T[ np.newaxis,: , :], Na, axis=0).T
blade_Gamma_2d = np.repeat(Gamma.T[ : , np.newaxis , :], Na, axis=1).T
Vt_avg = Wt
Va_avg = Wa
Vt_ind_avg = vt
Va_ind_avg = va
Va_ind_2d = np.repeat(va.T[ : , np.newaxis , :], Na, axis=1).T
Vt_ind_2d = np.repeat(vt.T[ : , np.newaxis , :], Na, axis=1).T
# thrust and torque derivatives on the blade.
blade_dT_dr = rho*(Gamma*(Wt-epsilon*Wa))
blade_dQ_dr = rho*(Gamma*(Wa+epsilon*Wt)*r)
thrust = np.atleast_2d((B * np.sum(blade_T_distribution, axis = 1))).T
torque = np.atleast_2d((B * np.sum(blade_Q_distribution, axis = 1))).T
power = omega*torque
# calculate coefficients
D = 2*R
Cq = torque/(rho_0*(n*n)*(D*D*D*D*D))
Ct = thrust/(rho_0*(n*n)*(D*D*D*D))
Cp = power/(rho_0*(n*n*n)*(D*D*D*D*D))
etap = V*thrust/power
# prevent things from breaking
Cq[Cq<0] = 0.
Ct[Ct<0] = 0.
Cp[Cp<0] = 0.
thrust[conditions.propulsion.throttle[:,0] <=0.0] = 0.0
power[conditions.propulsion.throttle[:,0] <=0.0] = 0.0
torque[conditions.propulsion.throttle[:,0] <=0.0] = 0.0
thrust[omega<0.0] = - thrust[omega<0.0]
thrust[omega==0.0] = 0.0
power[omega==0.0] = 0.0
torque[omega==0.0] = 0.0
Ct[omega==0.0] = 0.0
Cp[omega==0.0] = 0.0
etap[omega==0.0] = 0.0
# assign efficiency to network
conditions.propulsion.etap = etap
# store data
self.azimuthal_distribution = psi
results_conditions = Data
outputs = results_conditions(
number_radial_stations = Nr,
number_azimuthal_stations = Na,
disc_radial_distribution = r_dim_2d,
thrust_angle = theta,
speed_of_sound = conditions.freestream.speed_of_sound,
density = conditions.freestream.density,
velocity = Vv,
blade_tangential_induced_velocity = Vt_ind_avg,
blade_axial_induced_velocity = Va_ind_avg,
blade_tangential_velocity = Vt_avg,
blade_axial_velocity = Va_avg,
disc_tangential_induced_velocity = Vt_ind_2d,
disc_axial_induced_velocity = Va_ind_2d,
disc_tangential_velocity = Vt_2d,
disc_axial_velocity = Va_2d,
drag_coefficient = Cd,
lift_coefficient = Cl,
omega = omega,
disc_circulation = blade_Gamma_2d,
blade_dT_dr = blade_dT_dr,
blade_thrust_distribution = blade_T_distribution,
disc_thrust_distribution = blade_T_distribution_2d,
thrust_per_blade = thrust/B,
thrust_coefficient = Ct,
disc_azimuthal_distribution = psi_2d,
blade_dQ_dr = blade_dQ_dr,
blade_torque_distribution = blade_Q_distribution,
disc_torque_distribution = blade_Q_distribution_2d,
torque_per_blade = torque/B,
torque_coefficient = Cq,
power = power,
power_coefficient = Cp,
converged_inflow_ratio = lamdaw,
disc_local_angle_of_attack = alpha
)
return thrust, torque, power, Cp, outputs , etap
def spin(self, conditions):
""" Analyzes a propeller given geometry and operating conditions
Inputs:
hub radius
tip radius
rotation rate
freestream velocity
number of blades
number of stations
chord distribution
twist distribution
airfoil data
Outputs:
Power coefficient
Thrust coefficient
Assumptions:
Based on Qprop Theory document
"""
#Unpack
B = self.prop_attributes.number_blades
R = self.prop_attributes.tip_radius
Rh = self.prop_attributes.hub_radius
beta = self.prop_attributes.twist_distribution
c = self.prop_attributes.chord_distribution
omega1 = self.inputs.omega
rho = conditions.freestream.density[:, 0, None]
mu = conditions.freestream.dynamic_viscosity[:, 0, None]
Vv = conditions.frames.inertial.velocity_vector
a = conditions.freestream.speed_of_sound[:, 0, None]
T = conditions.freestream.temperature[:, 0, None]
theta = self.thrust_angle
tc = .12 # Thickness to chord
BB = B * B
BBB = BB * B
# Velocity in the Body frame
T_body2inertial = conditions.frames.body.transform_to_inertial
T_inertial2body = orientation_transpose(T_body2inertial)
V_body = orientation_product(T_inertial2body, Vv)
# Velocity transformed to the propulsor frame
body2thrust = np.array([[np.cos(theta), 0.,
np.sin(theta)], [0., 1., 0.],
[-np.sin(theta), 0.,
np.cos(theta)]])
T_body2thrust = orientation_transpose(
np.ones_like(T_body2inertial[:]) * body2thrust)
V_thrust = orientation_product(T_body2thrust, V_body)
# Now just use the aligned velocity
V = V_thrust[:, 0, None]
nu = mu / rho
tol = 1e-6 # Convergence tolerance
omega = omega1 * 1.0
omega = np.abs(omega)
######
# Enter airfoil data in a better way, there is currently Re and Ma scaling from DAE51 data
######
#Things that don't change with iteration
N = len(c) # Number of stations
chi0 = Rh / R # Where the propeller blade actually starts
chi = np.linspace(chi0, 1, N + 1) # Vector of nondimensional radii
chi = chi[0:N]
lamda = V / (omega * R) # Speed ratio
r = chi * R # Radial coordinate
pi = np.pi
pi2 = pi * pi
x = r * np.multiply(omega, 1 / V) # Nondimensional distance
n = omega / (2. * pi) # Cycles per second
J = V / (2. * R * n)
sigma = np.multiply(B * c, 1. / (2. * pi * r))
#I make the assumption that externally-induced velocity at the disk is zero
#This can be easily changed if needed in the future:
ua = 0.0
ut = 0.0
omegar = np.outer(omega, r)
Ua = np.outer((V + ua), np.ones_like(r))
Ut = omegar - ut
U = np.sqrt(Ua * Ua + Ut * Ut)
#Things that will change with iteration
size = (len(a), N)
#Setup a Newton iteration
psi = np.ones(size)
psiold = np.zeros(size)
diff = 1.
ii = 0
while (diff > tol):
sin_psi = np.sin(psi)
cos_psi = np.cos(psi)
Wa = 0.5 * Ua + 0.5 * U * sin_psi
Wt = 0.5 * Ut + 0.5 * U * cos_psi
#va = Wa - Ua
vt = Ut - Wt
alpha = beta - np.arctan2(Wa, Wt)
W = (Wa * Wa + Wt * Wt)**0.5
Ma = (W) / a #a is the speed of sound
#if np.any(Ma> 1.0):
#warn('Propeller blade tips are supersonic.', Warning)
lamdaw = r * Wa / (R * Wt)
# Limiter to keep from Nan-ing
lamdaw[lamdaw < 0.] = 0.
f = (B / 2.) * (1. - r / R) / lamdaw
piece = np.exp(-f)
arccos_piece = np.arccos(piece)
F = 2. * arccos_piece / pi
Gamma = vt * (4. * pi * r / B) * F * (1. + (4. * lamdaw * R /
(pi * B * r)) *
(4. * lamdaw * R /
(pi * B * r)))**0.5
# Estimate Cl max
Re = (W * c) / nu
#Cl_max_ref = -0.0009*tc**3 + 0.0217*tc**2 - 0.0442*tc + 0.7005
#Re_ref = 9.*10**6
#Cl1maxp = Cl_max_ref * ( Re / Re_ref ) **0.1
# Ok, from the airfoil data, given Re, Ma, alpha we need to find Cl
Cl = 2. * pi * alpha
# By 90 deg, it's totally stalled.
#Cl[Cl>Cl1maxp] = Cl1maxp[Cl>Cl1maxp]
Cl[alpha >= pi / 2] = 0.
## Scale for Mach, this is Karmen_Tsien
#Cl[Ma[:,:]<1.] = Cl[Ma[:,:]<1.]/((1-Ma[Ma[:,:]<1.]*Ma[Ma[:,:]<1.])**0.5+((Ma[Ma[:,:]<1.]*Ma[Ma[:,:]<1.])/(1+(1-Ma[Ma[:,:]<1.]*Ma[Ma[:,:]<1.])**0.5))*Cl[Ma<1.]/2)
## If the blade segments are supersonic, don't scale
#Cl[Ma[:,:]>=1.] = Cl[Ma[:,:]>=1.]
Rsquiggly = Gamma - 0.5 * W * c * Cl
#An analytical derivative for dR_dpsi, this is derived by taking a derivative of the above equations
#This was solved symbolically in Matlab and exported
f_wt_2 = 4 * Wt * Wt
f_wa_2 = 4 * Wa * Wa
Ucospsi = U * cos_psi
Usinpsi = U * sin_psi
Utcospsi = Ut * cos_psi
Uasinpsi = Ua * sin_psi
UapUsinpsi = (Ua + Usinpsi)
utpUcospsi = (Ut + Ucospsi)
utpUcospsi2 = utpUcospsi * utpUcospsi
UapUsinpsi2 = UapUsinpsi * UapUsinpsi
dR_dpsi = ((4. * U * r * arccos_piece * sin_psi *
((16. * UapUsinpsi2) /
(BB * pi2 * f_wt_2) + 1.)**(0.5)) / B -
(pi * U * (Ua * cos_psi - Ut * sin_psi) *
(beta - np.arctan(
(Wa + Wa) /
(Wt + Wt)))) / (2. * (f_wt_2 + f_wa_2)**(0.5)) +
(pi * U * (f_wt_2 + f_wa_2)**(0.5) *
(U + Utcospsi + Uasinpsi)) /
(2. * (f_wa_2 / (f_wt_2) + 1.) * utpUcospsi2) -
(4. * U * piece * ((16. * UapUsinpsi2) /
(BB * pi2 * f_wt_2) + 1.)**(0.5) *
(R - r) * (Ut / 2. - (Ucospsi) / 2.) *
(U + Utcospsi + Uasinpsi)) /
(f_wa_2 * (1. - np.exp(-(B * (Wt + Wt) * (R - r)) /
(r * (Wa + Wa))))**(0.5)) +
(128. * U * r * arccos_piece * (Wa + Wa) *
(Ut / 2. -
(Ucospsi) / 2.) * (U + Utcospsi + Uasinpsi)) /
(BBB * pi2 * utpUcospsi * utpUcospsi2 *
((16. * f_wa_2) / (BB * pi2 * f_wt_2) + 1.)**(0.5)))
dR_dpsi[np.isnan(dR_dpsi)] = 0.1
dpsi = -Rsquiggly / dR_dpsi
psi = psi + dpsi
diff = np.max(abs(psiold - psi))
psiold = psi
# If its really not going to converge
if np.any(psi > (pi * 85.0 / 180.)) and np.any(dpsi > 0.0):
print 'broke'
break
#There is also RE scaling
#This is an atrocious fit of DAE51 data at RE=50k for Cd
Cdval = (0.108 * (Cl * Cl * Cl * Cl) - 0.2612 *
(Cl * Cl * Cl) + 0.181 *
(Cl * Cl) - 0.0139 * Cl + 0.0278) * ((50000. / Re)**0.2)
Cdval[alpha >= pi / 2] = 2.
#More Cd scaling from Mach from AA241ab notes for turbulent skin friction
Tw_Tinf = 1. + 1.78 * (Ma * Ma)
Tp_Tinf = 1. + 0.035 * (Ma * Ma) + 0.45 * (Tw_Tinf - 1.)
Tp = (Tp_Tinf) * T
Rp_Rinf = (Tp_Tinf**2.5) * (Tp + 110.4) / (T + 110.4)
Cd = ((1 / Tp_Tinf) * (1 / Rp_Rinf)**0.2) * Cdval
epsilon = Cd / Cl
epsilon[epsilon == np.inf] = 10.
deltar = (r[1] - r[0])
thrust = rho * B * (np.sum(Gamma * (Wt - epsilon * Wa) * deltar,
axis=1)[:, None])
torque = rho * B * np.sum(Gamma * (Wa + epsilon * Wt) * r * deltar,
axis=1)[:, None]
power = torque * omega
D = 2 * R
Cp = power / (rho * (n * n * n) * (D * D * D * D * D))
thrust[conditions.propulsion.throttle[:, 0] <= 0.0] = 0.0
power[conditions.propulsion.throttle[:, 0] <= 0.0] = 0.0
thrust[omega1 < 0.0] = -thrust[omega1 < 0.0]
etap = V * thrust / power
conditions.propulsion.etap = etap
# calculating Activity Factor (per blade)
#AF = 100000./16. * np.trapz((c/D) * (r/R)**3, x=r/R)
AF = (10. / D)**5. * np.trapz(c * r**3, x=r)
# store data
results_conditions = Results
conditions.propulsion.acoustic_outputs = results_conditions(
number_sections=N,
r0=r,
airfoil_chord=c,
blades_number=B,
propeller_diameter=D,
drag_coefficient=Cd,
lift_coefficient=Cl,
rpm=omega,
velocity=V,
thrust=thrust,
hp=power,
blade_activity_factor=AF,
)
return thrust, torque, power, Cp
def update_orientations(segment):
""" Updates the orientation of the vehicle throughout the mission for each relevant axis
Assumptions:
This assumes the vehicle has 3 frames: inertial, body, and wind. There also contains bits for stability axis which are not used. Creates tensors and solves for alpha and beta.
Inputs:
segment.state.conditions:
frames.inertial.velocity_vector [meters/second]
frames.body.inertial_rotations [Radians]
segment.analyses.planet.features.mean_radius [meters]
state.numerics.time.integrate [float]
Outputs:
segment.state.conditions:
aerodynamics.angle_of_attack [Radians]
aerodynamics.side_slip_angle [Radians]
aerodynamics.roll_angle [Radians]
frames.body.transform_to_inertial [Radians]
frames.wind.body_rotations [Radians]
frames.wind.transform_to_inertial [Radians]
Properties Used:
N/A
"""
# unpack
conditions = segment.state.conditions
V_inertial = conditions.frames.inertial.velocity_vector
body_inertial_rotations = conditions.frames.body.inertial_rotations
# ------------------------------------------------------------------
# Body Frame
# ------------------------------------------------------------------
# body frame rotations
phi = body_inertial_rotations[:, 0, None]
theta = body_inertial_rotations[:, 1, None]
psi = body_inertial_rotations[:, 2, None]
# body frame tranformation matrices
T_inertial2body = angles_to_dcms(body_inertial_rotations, (2, 1, 0))
T_body2inertial = orientation_transpose(T_inertial2body)
# transform inertial velocity to body frame
V_body = orientation_product(T_inertial2body, V_inertial)
# project inertial velocity into body x-z plane
V_stability = V_body * 1.
V_stability[:, 1] = 0
V_stability_magnitude = np.sqrt(np.sum(V_stability**2, axis=1))[:, None]
# calculate angle of attack
alpha = np.arctan2(V_stability[:, 2], V_stability[:, 0])[:, None]
# calculate side slip
beta = np.arctan2(V_body[:, 1], V_stability_magnitude[:, 0])[:, None]
# pack aerodynamics angles
conditions.aerodynamics.angle_of_attack[:, 0] = alpha[:, 0]
conditions.aerodynamics.side_slip_angle[:, 0] = -beta[:, 0]
conditions.aerodynamics.roll_angle[:, 0] = phi[:, 0]
# pack transformation tensor
conditions.frames.body.transform_to_inertial = T_body2inertial
# ------------------------------------------------------------------
# Wind Frame
# ------------------------------------------------------------------
# back calculate wind frame rotations
wind_body_rotations = body_inertial_rotations * 0.
wind_body_rotations[:, 0] = 0 # no roll in wind frame
wind_body_rotations[:, 1] = alpha[:, 0] # theta is angle of attack
wind_body_rotations[:, 2] = beta[:, 0] # psi is side slip angle
# wind frame tranformation matricies
T_wind2body = angles_to_dcms(wind_body_rotations, (2, 1, 0))
T_body2wind = orientation_transpose(T_wind2body)
T_wind2inertial = orientation_product(T_wind2body, T_body2inertial)
# pack wind rotations
conditions.frames.wind.body_rotations = wind_body_rotations
# pack transformation tensor
conditions.frames.wind.transform_to_inertial = T_wind2inertial
return
def spin(self, conditions):
"""Analyzes a rotor given geometry and operating conditions.
Assumptions:
per source
Source:
Drela, M. "Qprop Formulation", MIT AeroAstro, June 2006
http://web.mit.edu/drela/Public/web/qprop/qprop_theory.pdf
Leishman, Gordon J. Principles of helicopter aerodynamics
Cambridge university press, 2006.
Inputs:
self.inputs.omega [radian/s]
conditions.freestream.
density [kg/m^3]
dynamic_viscosity [kg/(m-s)]
speed_of_sound [m/s]
temperature [K]
conditions.frames.
body.transform_to_inertial (rotation matrix)
inertial.velocity_vector [m/s]
conditions.propulsion.
throttle [-]
Outputs:
conditions.propulsion.outputs.
number_radial_stations [-]
number_azimuthal_stations [-]
disc_radial_distribution [m]
thrust_angle [rad]
speed_of_sound [m/s]
density [kg/m-3]
velocity [m/s]
disc_tangential_induced_velocity [m/s]
disc_axial_induced_velocity [m/s]
disc_tangential_velocity [m/s]
disc_axial_velocity [m/s]
drag_coefficient [-]
lift_coefficient [-]
omega [rad/s]
disc_circulation [-]
blade_dQ_dR [N/m]
blade_dT_dr [N]
blade_thrust_distribution [N]
disc_thrust_distribution [N]
thrust_per_blade [N]
thrust_coefficient [-]
azimuthal_distribution [rad]
disc_azimuthal_distribution [rad]
blade_dQ_dR [N]
blade_dQ_dr [Nm]
blade_torque_distribution [Nm]
disc_torque_distribution [Nm]
torque_per_blade [Nm]
torque_coefficient [-]
power [W]
power_coefficient [-]
Properties Used:
self.
number_of_blades [-]
tip_radius [m]
hub_radius [m]
twist_distribution [radians]
chord_distribution [m]
mid_chord_alignment [m]
thrust_angle [radians]
"""
#Unpack
B = self.number_of_blades
R = self.tip_radius
Rh = self.hub_radius
beta_0 = self.twist_distribution
c = self.chord_distribution
chi = self.radius_distribution
omega = self.inputs.omega
a_geo = self.airfoil_geometry
a_loc = self.airfoil_polar_stations
cl_sur = self.airfoil_cl_surrogates
cd_sur = self.airfoil_cd_surrogates
tc = self.thickness_to_chord
ua = self.induced_hover_velocity
VTOL = self.VTOL_flag
rho = conditions.freestream.density[:, 0, None]
mu = conditions.freestream.dynamic_viscosity[:, 0, None]
Vv = conditions.frames.inertial.velocity_vector
a = conditions.freestream.speed_of_sound[:, 0, None]
T = conditions.freestream.temperature[:, 0, None]
pitch_c = self.pitch_command
theta = self.thrust_angle
Na = self.number_azimuthal_stations
BB = B * B
BBB = BB * B
# calculate total blade pitch
total_blade_pitch = beta_0 + pitch_c
# Velocity in the Body frame
T_body2inertial = conditions.frames.body.transform_to_inertial
T_inertial2body = orientation_transpose(T_body2inertial)
V_body = orientation_product(T_inertial2body, Vv)
body2thrust = np.array([[np.cos(theta), 0.,
np.sin(theta)], [0., 1., 0.],
[-np.sin(theta), 0.,
np.cos(theta)]])
T_body2thrust = orientation_transpose(
np.ones_like(T_body2inertial[:]) * body2thrust)
V_thrust = orientation_product(T_body2thrust, V_body)
if VTOL:
V = V_thrust[:, 0, None] + ua
else:
V = V_thrust[:, 0, None]
ut = np.zeros_like(V)
#Things that don't change with iteration
Nr = len(c) # Number of stations radially
ctrl_pts = len(Vv)
# set up non dimensional radial distribution
chi = self.radius_distribution / R
omega = np.abs(omega)
r = chi * R # Radial coordinate
pi = np.pi
pi2 = pi * pi
n = omega / (2. * pi) # Cycles per second
nu = mu / rho
# azimuth distribution
psi = np.linspace(0, 2 * pi, Na + 1)[:-1]
psi_2d = np.tile(np.atleast_2d(psi).T, (1, Nr))
psi_2d = np.repeat(psi_2d[np.newaxis, :, :], ctrl_pts, axis=0)
azimuth_2d = np.repeat(np.atleast_2d(psi).T[np.newaxis, :, :],
Na,
axis=0).T
# 2 dimensiona radial distribution non dimensionalized
chi_2d = np.tile(chi, (Na, 1))
chi_2d = np.repeat(chi_2d[np.newaxis, :, :], ctrl_pts, axis=0)
r_dim_2d = np.tile(r, (Na, 1))
r_dim_2d = np.repeat(r_dim_2d[np.newaxis, :, :], ctrl_pts, axis=0)
# Things that will change with iteration
size = (len(a), Nr)
omegar = np.outer(omega, r)
Ua = np.outer((V + ua), np.ones_like(r))
Ut = omegar - ut
U = np.sqrt(Ua * Ua + Ut * Ut)
beta = total_blade_pitch
# Setup a Newton iteration
PSI = np.ones(size)
PSIold = np.zeros(size)
diff = 1.
ii = 0
broke = False
tol = 1e-6 # Convergence tolerance
while (diff > tol):
sin_psi = np.sin(PSI)
cos_psi = np.cos(PSI)
Wa = 0.5 * Ua + 0.5 * U * sin_psi
Wt = 0.5 * Ut + 0.5 * U * cos_psi
va = Wa - Ua
vt = Ut - Wt
alpha = beta - np.arctan2(Wa, Wt)
W = (Wa * Wa + Wt * Wt)**0.5
Ma = (W) / a # a is the speed of sound
lamdaw = r * Wa / (R * Wt)
# Limiter to keep from Nan-ing
lamdaw[lamdaw < 0.] = 0.
f = (B / 2.) * (1. - r / R) / lamdaw
f[f < 0.] = 0.
piece = np.exp(-f)
arccos_piece = np.arccos(piece)
F = 2. * arccos_piece / pi
Gamma = vt * (4. * pi * r / B) * F * (1. + (4. * lamdaw * R /
(pi * B * r)) *
(4. * lamdaw * R /
(pi * B * r)))**0.5
Re = (W * c) / nu
# If rotor airfoils are defined, using airfoil surrogate
if a_loc != None:
# Compute blade Cl and Cd distribution from the airfoil data
Cl = np.zeros((ctrl_pts, Nr))
Cdval = np.zeros((ctrl_pts, Nr))
dim_sur = len(cl_sur)
for jj in range(dim_sur):
Cl_af = cl_sur[a_geo[jj]](Re, alpha, grid=False)
Cdval_af = cd_sur[a_geo[jj]](Re, alpha, grid=False)
locs = np.where(np.array(a_loc) == jj)
Cl[:, locs] = Cl_af[:, locs]
Cdval[:, locs] = Cdval_af[:, locs]
else:
# Estimate Cl max
Cl_max_ref = -0.0009 * tc**3 + 0.0217 * tc**2 - 0.0442 * tc + 0.7005
Re_ref = 9. * 10**6
Cl1maxp = Cl_max_ref * (Re / Re_ref)**0.1
# If not airfoil polar provided, use 2*pi as lift curve slope
Cl = 2. * pi * alpha
# By 90 deg, it's totally stalled.
Cl[Cl > Cl1maxp] = Cl1maxp[
Cl >
Cl1maxp] # This line of code is what changed the regression testing
Cl[alpha >= pi / 2] = 0.
# Scale for Mach, this is Karmen_Tsien
Cl[Ma[:, :] < 1.] = Cl[Ma[:, :] < 1.] / (
(1 - Ma[Ma[:, :] < 1.] * Ma[Ma[:, :] < 1.])**0.5 +
((Ma[Ma[:, :] < 1.] * Ma[Ma[:, :] < 1.]) /
(1 + (1 - Ma[Ma[:, :] < 1.] * Ma[Ma[:, :] < 1.])**0.5)) *
Cl[Ma < 1.] / 2)
# If the blade segments are supersonic, don't scale
Cl[Ma[:, :] >= 1.] = Cl[Ma[:, :] >= 1.]
#This is an atrocious fit of DAE51 data at RE=50k for Cd
Cdval = (0.108 * (Cl * Cl * Cl * Cl) - 0.2612 *
(Cl * Cl * Cl) + 0.181 *
(Cl * Cl) - 0.0139 * Cl + 0.0278) * (
(50000. / Re)**0.2)
Cdval[alpha >= pi / 2] = 2.
Rsquiggly = Gamma - 0.5 * W * c * Cl
# An analytical derivative for dR_dpsi, this is derived by taking a derivative of the above equations
# This was solved symbolically in Matlab and exported
f_wt_2 = 4 * Wt * Wt
f_wa_2 = 4 * Wa * Wa
Ucospsi = U * cos_psi
Usinpsi = U * sin_psi
Utcospsi = Ut * cos_psi
Uasinpsi = Ua * sin_psi
UapUsinpsi = (Ua + Usinpsi)
utpUcospsi = (Ut + Ucospsi)
utpUcospsi2 = utpUcospsi * utpUcospsi
UapUsinpsi2 = UapUsinpsi * UapUsinpsi
dR_dpsi = ((4. * U * r * arccos_piece * sin_psi *
((16. * UapUsinpsi2) /
(BB * pi2 * f_wt_2) + 1.)**(0.5)) / B -
(pi * U * (Ua * cos_psi - Ut * sin_psi) *
(beta - np.arctan(
(Wa + Wa) /
(Wt + Wt)))) / (2. * (f_wt_2 + f_wa_2)**(0.5)) +
(pi * U * (f_wt_2 + f_wa_2)**(0.5) *
(U + Utcospsi + Uasinpsi)) /
(2. * (f_wa_2 / (f_wt_2) + 1.) * utpUcospsi2) -
(4. * U * piece * ((16. * UapUsinpsi2) /
(BB * pi2 * f_wt_2) + 1.)**(0.5) *
(R - r) * (Ut / 2. - (Ucospsi) / 2.) *
(U + Utcospsi + Uasinpsi)) /
(f_wa_2 * (1. - np.exp(-(B * (Wt + Wt) * (R - r)) /
(r * (Wa + Wa))))**(0.5)) +
(128. * U * r * arccos_piece * (Wa + Wa) *
(Ut / 2. -
(Ucospsi) / 2.) * (U + Utcospsi + Uasinpsi)) /
(BBB * pi2 * utpUcospsi * utpUcospsi2 *
((16. * f_wa_2) / (BB * pi2 * f_wt_2) + 1.)**(0.5)))
dR_dpsi[np.isnan(dR_dpsi)] = 0.1
dpsi = -Rsquiggly / dR_dpsi
PSI = PSI + dpsi
diff = np.max(abs(PSIold - PSI))
PSIold = PSI
# omega = 0, do not run BEMT convergence loop
if all(omega[:, 0]) == 0.:
break
# If its really not going to converge
if np.any(PSI > pi / 2) and np.any(dpsi > 0.0):
print("Rotor BEMT did not converge to a solution")
break
ii += 1
if ii > 10000:
broke = True
print(
"Rotor BEMT did not converge to a solution (Iteration Limit)"
)
break
# More Cd scaling from Mach from AA241ab notes for turbulent skin friction
Tw_Tinf = 1. + 1.78 * (Ma * Ma)
Tp_Tinf = 1. + 0.035 * (Ma * Ma) + 0.45 * (Tw_Tinf - 1.)
Tp = (Tp_Tinf) * T
Rp_Rinf = (Tp_Tinf**2.5) * (Tp + 110.4) / (T + 110.4)
Cd = ((1 / Tp_Tinf) * (1 / Rp_Rinf)**0.2) * Cdval
epsilon = Cd / Cl
epsilon[epsilon == np.inf] = 10.
deltar = (r[1] - r[0])
deltachi = (chi[1] - chi[0])
blade_T_distribution = rho * (Gamma * (Wt - epsilon * Wa)) * deltar
blade_Q_distribution = rho * (Gamma * (Wa + epsilon * Wt) * r) * deltar
thrust = rho * B * (np.sum(Gamma * (Wt - epsilon * Wa) * deltar,
axis=1)[:, None])
torque = rho * B * np.sum(Gamma * (Wa + epsilon * Wt) * r * deltar,
axis=1)[:, None]
power = omega * torque
Va_2d = np.repeat(Wa.T[:, np.newaxis, :], Na, axis=1).T
Vt_2d = np.repeat(Wt.T[:, np.newaxis, :], Na, axis=1).T
Va_ind_2d = np.repeat(va.T[:, np.newaxis, :], Na, axis=1).T
Vt_ind_2d = np.repeat(vt.T[:, np.newaxis, :], Na, axis=1).T
blade_T_distribution_2d = np.repeat(
blade_T_distribution.T[np.newaxis, :, :], Na, axis=0).T
blade_Q_distribution_2d = np.repeat(
blade_Q_distribution.T[np.newaxis, :, :], Na, axis=0).T
blade_Gamma_2d = np.repeat(Gamma.T[:, np.newaxis, :], Na, axis=1).T
# thrust and torque derivatives on the blade.
blade_dT_dr = rho * (Gamma * (Wt - epsilon * Wa))
blade_dQ_dr = rho * (Gamma * (Wa + epsilon * Wt) * r)
Vt_ind_avg = vt
Va_ind_avg = va
Vt_avg = Wt
Va_avg = Wa
# calculate coefficients
D = 2 * R
Cq = torque / (rho * (n * n) * (D * D * D * D * D))
Ct = thrust / (rho * (n * n) * (D * D * D * D))
Cp = power / (rho * (n * n * n) * (D * D * D * D * D))
etap = V * thrust / power # efficiency
# prevent things from breaking
Cq[Cq < 0] = 0.
Ct[Ct < 0] = 0.
Cp[Cp < 0] = 0.
thrust[conditions.propulsion.throttle[:, 0] <= 0.0] = 0.0
power[conditions.propulsion.throttle[:, 0] <= 0.0] = 0.0
torque[conditions.propulsion.throttle[:, 0] <= 0.0] = 0.0
thrust[omega < 0.0] = -thrust[omega < 0.0]
thrust[omega == 0.0] = 0.0
power[omega == 0.0] = 0.0
torque[omega == 0.0] = 0.0
Ct[omega == 0.0] = 0.0
Cp[omega == 0.0] = 0.0
etap[omega == 0.0] = 0.0
# assign efficiency to network
conditions.propulsion.etap = etap
# store data
self.azimuthal_distribution = psi
results_conditions = Data
outputs = results_conditions(
number_radial_stations=Nr,
number_azimuthal_stations=Na,
disc_radial_distribution=r_dim_2d,
thrust_angle=theta,
speed_of_sound=conditions.freestream.speed_of_sound,
density=conditions.freestream.density,
velocity=Vv,
blade_tangential_induced_velocity=Vt_ind_avg,
blade_axial_induced_velocity=Va_ind_avg,
blade_tangential_velocity=Vt_avg,
blade_axial_velocity=Va_avg,
disc_tangential_induced_velocity=Vt_ind_2d,
disc_axial_induced_velocity=Va_ind_2d,
disc_tangential_velocity=Vt_2d,
disc_axial_velocity=Va_2d,
drag_coefficient=Cd,
lift_coefficient=Cl,
omega=omega,
disc_circulation=blade_Gamma_2d,
blade_dT_dr=blade_dT_dr,
blade_thrust_distribution=blade_T_distribution,
disc_thrust_distribution=blade_T_distribution_2d,
thrust_per_blade=thrust / B,
thrust_coefficient=Ct,
disc_azimuthal_distribution=azimuth_2d,
blade_dQ_dr=blade_dQ_dr,
blade_torque_distribution=blade_Q_distribution,
disc_torque_distribution=blade_Q_distribution_2d,
torque_per_blade=torque / B,
torque_coefficient=Cq,
power=power,
power_coefficient=Cp,
)
return thrust, torque, power, Cp, outputs, etap
def spin(self,conditions):
"""Analyzes a propeller given geometry and operating conditions.
Assumptions:
per source
Source:
Drela, M. "Qprop Formulation", MIT AeroAstro, June 2006
http://web.mit.edu/drela/Public/web/qprop/qprop_theory.pdf
Inputs:
self.inputs.omega [radian/s]
conditions.freestream.
density [kg/m^3]
dynamic_viscosity [kg/(m-s)]
speed_of_sound [m/s]
temperature [K]
conditions.frames.
body.transform_to_inertial (rotation matrix)
inertial.velocity_vector [m/s]
conditions.propulsion.
throttle [-]
Outputs:
conditions.propulsion.acoustic_outputs.
number_sections [-]
r0 [m]
airfoil_chord [m]
blades_number [-]
propeller_diameter [m]
drag_coefficient [-]
lift_coefficient [-]
omega [radian/s]
velocity [m/s]
thrust [N]
power [W]
mid_chord_aligment [m] (distance from the mid chord to the line axis out of the center of the blade)
conditions.propulsion.etap [-]
thrust [N]
torque [Nm]
power [W]
Cp [-] (coefficient of power)
Properties Used:
self.
number_blades [-]
tip_radius [m]
hub_radius [m]
twist_distribution [radians]
chord_distribution [m]
mid_chord_aligment [m] (distance from the mid chord to the line axis out of the center of the blade)
thrust_angle [radians]
"""
#Unpack
B = self.number_blades
R = self.tip_radius
Rh = self.hub_radius
beta = self.twist_distribution
c = self.chord_distribution
chi = self.radius_distribution
omega = self.inputs.omega
a_geo = self.airfoil_geometry
a_pol = self.airfoil_polars
a_loc = self.airfoil_polar_stations
rho = conditions.freestream.density[:,0,None]
mu = conditions.freestream.dynamic_viscosity[:,0,None]
Vv = conditions.frames.inertial.velocity_vector
Vh = self.induced_hover_velocity
a = conditions.freestream.speed_of_sound[:,0,None]
T = conditions.freestream.temperature[:,0,None]
theta = self.thrust_angle
tc = self.thickness_to_chord
sigma = self.blade_solidity
BB = B*B
BBB = BB*B
# Velocity in the Body frame
T_body2inertial = conditions.frames.body.transform_to_inertial
T_inertial2body = orientation_transpose(T_body2inertial)
V_body = orientation_product(T_inertial2body,Vv)
body2thrust = np.array([[np.cos(theta), 0., np.sin(theta)],[0., 1., 0.], [-np.sin(theta), 0., np.cos(theta)]])
T_body2thrust = orientation_transpose(np.ones_like(T_body2inertial[:])*body2thrust)
V_thrust = orientation_product(T_body2thrust,V_body)
# Now just use the aligned velocity
V = V_thrust[:,0,None]
ua = np.zeros_like(V)
ut = np.zeros_like(V)
nu = mu/rho
tol = 1e-5 # Convergence tolerance
#Things that don't change with iteration
N = len(c) # Number of stations
if a_pol != None and a_loc != None:
airfoil_polars = Data()
# check dimension of section
if len(a_loc) != N:
raise AssertionError('Dimension of airfoil sections must be equal to number of stations on propeller')
# compute airfoil polars for airfoils
airfoil_polars = compute_airfoil_polars(self, a_geo, a_pol)
airfoil_cl = airfoil_polars.lift_coefficients
airfoil_cd = airfoil_polars.drag_coefficients
AoA_sweep = airfoil_polars.angle_of_attacks
if self.radius_distribution is None:
chi0 = Rh/R # Where the propeller blade actually starts
chi = np.linspace(chi0,1,N+1) # Vector of nondimensional radii
chi = chi[0:N]
lamda = V/(omega*R) # Speed ratio
r = chi*R # Radial coordinate
pi = np.pi
pi2 = pi*pi
x = r*np.multiply(omega,1/V) # Nondimensional distance
n = omega/(2.*pi) # Cycles per second
J = V/(2.*R*n)
omegar = np.outer(omega,r)
Ua = np.outer((V + ua),np.ones_like(r))
Ut = omegar - ut
U = np.sqrt(Ua*Ua + Ut*Ut)
#Things that will change with iteration
size = (len(a),N)
Cl = np.zeros((1,N))
#Setup a Newton iteration
psi = np.ones(size)
psiold = np.zeros(size)
diff = 1.
ii = 0
broke = False
while (diff>tol):
sin_psi = np.sin(psi)
cos_psi = np.cos(psi)
Wa = 0.5*Ua + 0.5*U*sin_psi
Wt = 0.5*Ut + 0.5*U*cos_psi
va = Wa - Ua
vt = Ut - Wt
alpha = beta - np.arctan2(Wa,Wt)
W = (Wa*Wa + Wt*Wt)**0.5
Ma = (W)/a #a is the speed of sound
lamdaw = r*Wa/(R*Wt)
# Limiter to keep from Nan-ing
lamdaw[lamdaw<0.] = 0.
f = (B/2.)*(1.-r/R)/lamdaw
piece = np.exp(-f)
arccos_piece = np.arccos(piece)
F = 2.*arccos_piece/pi
Gamma = vt*(4.*pi*r/B)*F*(1.+(4.*lamdaw*R/(pi*B*r))*(4.*lamdaw*R/(pi*B*r)))**0.5
# Estimate Cl max
Re = (W*c)/nu
Cl_max_ref = -0.0009*tc**3 + 0.0217*tc**2 - 0.0442*tc + 0.7005
Re_ref = 9.*10**6
Cl1maxp = Cl_max_ref * ( Re / Re_ref ) **0.1
# Compute blade CL distribution from the airfoil data
if a_pol != None and a_loc != None:
for k in range(N):
Cl[0,k] = np.interp(alpha[0,k],AoA_sweep,airfoil_cl[a_loc[k]])
else:
# If not airfoil polar provided, use 2*pi as lift curve slope
Cl = 2.*pi*alpha
# By 90 deg, it's totally stalled.
Cl[Cl>Cl1maxp] = Cl1maxp[Cl>Cl1maxp] # This line of code is what changed the regression testing
Cl[alpha>=pi/2] = 0.
# Scale for Mach, this is Karmen_Tsien
Cl[Ma[:,:]<1.] = Cl[Ma[:,:]<1.]/((1-Ma[Ma[:,:]<1.]*Ma[Ma[:,:]<1.])**0.5+((Ma[Ma[:,:]<1.]*Ma[Ma[:,:]<1.])/(1+(1-Ma[Ma[:,:]<1.]*Ma[Ma[:,:]<1.])**0.5))*Cl[Ma<1.]/2)
# If the blade segments are supersonic, don't scale
Cl[Ma[:,:]>=1.] = Cl[Ma[:,:]>=1.]
Rsquiggly = Gamma - 0.5*W*c*Cl
#An analytical derivative for dR_dpsi, this is derived by taking a derivative of the above equations
#This was solved symbolically in Matlab and exported
f_wt_2 = 4*Wt*Wt
f_wa_2 = 4*Wa*Wa
Ucospsi = U*cos_psi
Usinpsi = U*sin_psi
Utcospsi = Ut*cos_psi
Uasinpsi = Ua*sin_psi
UapUsinpsi = (Ua + Usinpsi)
utpUcospsi = (Ut + Ucospsi)
utpUcospsi2 = utpUcospsi*utpUcospsi
UapUsinpsi2 = UapUsinpsi*UapUsinpsi
dR_dpsi = ((4.*U*r*arccos_piece*sin_psi*((16.*UapUsinpsi2)/(BB*pi2*f_wt_2) + 1.)**(0.5))/B -
(pi*U*(Ua*cos_psi - Ut*sin_psi)*(beta - np.arctan((Wa+Wa)/(Wt+Wt))))/(2.*(f_wt_2 + f_wa_2)**(0.5))
+ (pi*U*(f_wt_2 +f_wa_2)**(0.5)*(U + Utcospsi + Uasinpsi))/(2.*(f_wa_2/(f_wt_2) + 1.)*utpUcospsi2)
- (4.*U*piece*((16.*UapUsinpsi2)/(BB*pi2*f_wt_2) + 1.)**(0.5)*(R - r)*(Ut/2. -
(Ucospsi)/2.)*(U + Utcospsi + Uasinpsi ))/(f_wa_2*(1. - np.exp(-(B*(Wt+Wt)*(R -
r))/(r*(Wa+Wa))))**(0.5)) + (128.*U*r*arccos_piece*(Wa+Wa)*(Ut/2. - (Ucospsi)/2.)*(U +
Utcospsi + Uasinpsi ))/(BBB*pi2*utpUcospsi*utpUcospsi2*((16.*f_wa_2)/(BB*pi2*f_wt_2) + 1.)**(0.5)))
dR_dpsi[np.isnan(dR_dpsi)] = 0.1
dpsi = -Rsquiggly/dR_dpsi
psi = psi + dpsi
diff = np.max(abs(psiold-psi))
psiold = psi
# If its really not going to converge
if np.any(psi>pi/2) and np.any(dpsi>0.0):
break
ii+=1
if ii>2000:
broke = True
break
#There is also RE scaling
#This is an atrocious fit of DAE51 data at RE=50k for Cd
Cdval = (0.108*(Cl*Cl*Cl*Cl)-0.2612*(Cl*Cl*Cl)+0.181*(Cl*Cl)-0.0139*Cl+0.0278)*((50000./Re)**0.2)
Cdval[alpha>=pi/2] = 2.
#More Cd scaling from Mach from AA241ab notes for turbulent skin friction
Tw_Tinf = 1. + 1.78*(Ma*Ma)
Tp_Tinf = 1. + 0.035*(Ma*Ma) + 0.45*(Tw_Tinf-1.)
Tp = (Tp_Tinf)*T
Rp_Rinf = (Tp_Tinf**2.5)*(Tp+110.4)/(T+110.4)
Cd = ((1/Tp_Tinf)*(1/Rp_Rinf)**0.2)*Cdval
epsilon = Cd/Cl
epsilon[epsilon==np.inf] = 10.
deltar = (r[1]-r[0])
thrust = rho*B*(np.sum(Gamma*(Wt-epsilon*Wa)*deltar,axis=1)[:,None])
torque = rho*B*np.sum(Gamma*(Wa+epsilon*Wt)*r*deltar,axis=1)[:,None]
D = 2*R
Ct = thrust/(rho*(n*n)*(D*D*D*D))
Ct[Ct<0] = 0. #prevent things from breaking
kappa = self.induced_power_factor
Cd0 = self.profile_drag_coefficient
Cp = np.zeros_like(Ct)
power = np.zeros_like(Ct)
for i in range(len(Vv)):
if -1. <Vv[i][0] <1.: # vertical/axial flight
Cp[i] = (kappa*(Ct[i]**1.5)/(2**.5))+sigma*Cd0/8.
power[i] = Cp[i]*(rho[i]*(n[i]*n[i]*n[i])*(D*D*D*D*D))
torque[i] = power[i]/omega[i]
else:
power[i] = torque[i]*omega[i]
Cp[i] = power[i]/(rho[i]*(n[i]*n[i]*n[i])*(D*D*D*D*D))
# torque coefficient
Cq = torque/(rho*(n*n)*(D*D*D*D)*R)
thrust[conditions.propulsion.throttle[:,0] <=0.0] = 0.0
power[conditions.propulsion.throttle[:,0] <=0.0] = 0.0
torque[conditions.propulsion.throttle[:,0] <=0.0] = 0.0
thrust[omega<0.0] = - thrust[omega<0.0]
etap = V*thrust/power
conditions.propulsion.etap = etap
# store data
results_conditions = Data
outputs = results_conditions(
num_blades = B,
rotor_radius = R,
rotor_diameter = D,
number_sections = N,
radius_distribution = np.linspace(Rh ,R, N),
chord_distribution = c,
twist_distribution = beta,
normalized_radial_distribution = r,
thrust_angle = theta,
speed_of_sound = conditions.freestream.speed_of_sound,
density = conditions.freestream.density,
velocity = Vv,
tangential_velocity_distribution = vt,
axial_velocity_distribution = va,
drag_coefficient = Cd,
lift_coefficient = Cl,
omega = omega,
dT_dR = rho*(Gamma*(Wt-epsilon*Wa)),
dT_dr = rho*(Gamma*(Wt-epsilon*Wa))*R,
thrust_distribution = rho*(Gamma*(Wt-epsilon*Wa))*deltar,
thrust_per_blade = thrust/B,
thrust_coefficient = Ct,
dQ_dR = rho*(Gamma*(Wa+epsilon*Wt)*r),
dQ_dr = rho*(Gamma*(Wa+epsilon*Wt)*r)*R,
torque_distribution = rho*(Gamma*(Wa+epsilon*Wt)*r)*deltar,
torque_per_blade = torque/B,
torque_coefficient = Cq,
power = power,
power_coefficient = Cp,
mid_chord_aligment = self.mid_chord_aligment
)
return thrust, torque, power, Cp, outputs , etap
def update_orientations(segment, state):
# unpack
conditions = state.conditions
V_inertial = conditions.frames.inertial.velocity_vector
body_inertial_rotations = conditions.frames.body.inertial_rotations
# ------------------------------------------------------------------
# Body Frame
# ------------------------------------------------------------------
# body frame rotations
phi = body_inertial_rotations[:, 0, None]
theta = body_inertial_rotations[:, 1, None]
psi = body_inertial_rotations[:, 2, None]
# body frame tranformation matrices
T_inertial2body = angles_to_dcms(body_inertial_rotations, (2, 1, 0))
T_body2inertial = orientation_transpose(T_inertial2body)
# transform inertial velocity to body frame
V_body = orientation_product(T_inertial2body, V_inertial)
# project inertial velocity into body x-z plane
V_stability = V_body
V_stability[:, 1] = 0
V_stability_magnitude = np.sqrt(np.sum(V_stability**2, axis=1))[:, None]
#V_stability_direction = V_stability / V_stability_magnitude
# calculate angle of attack
alpha = np.arctan2(V_stability[:, 2], V_stability[:, 0])[:, None]
# calculate side slip
beta = np.arctan2(V_body[:, 1], V_stability_magnitude[:, 0])[:, None]
# pack aerodynamics angles
conditions.aerodynamics.angle_of_attack[:, 0] = alpha[:, 0]
conditions.aerodynamics.side_slip_angle[:, 0] = beta[:, 0]
conditions.aerodynamics.roll_angle[:, 0] = phi[:, 0]
# pack transformation tensor
conditions.frames.body.transform_to_inertial = T_body2inertial
# ------------------------------------------------------------------
# Wind Frame
# ------------------------------------------------------------------
# back calculate wind frame rotations
wind_body_rotations = body_inertial_rotations * 0.
wind_body_rotations[:, 0] = 0 # no roll in wind frame
wind_body_rotations[:, 1] = alpha[:, 0] # theta is angle of attack
wind_body_rotations[:, 2] = beta[:, 0] # psi is side slip angle
# wind frame tranformation matricies
T_wind2body = angles_to_dcms(wind_body_rotations, (2, 1, 0))
T_body2wind = orientation_transpose(T_wind2body)
T_wind2inertial = orientation_product(T_wind2body, T_body2inertial)
# pack wind rotations
conditions.frames.wind.body_rotations = wind_body_rotations
# pack transformation tensor
conditions.frames.wind.transform_to_inertial = T_wind2inertial
return
def spin(self, conditions):
"""Analyzes a general rotor given geometry and operating conditions.
Assumptions:
per source
Source:
Drela, M. "Qprop Formulation", MIT AeroAstro, June 2006
http://web.mit.edu/drela/Public/web/qprop/qprop_theory.pdf
Leishman, Gordon J. Principles of helicopter aerodynamics
Cambridge university press, 2006.
Inputs:
self.inputs.omega [radian/s]
conditions.freestream.
density [kg/m^3]
dynamic_viscosity [kg/(m-s)]
speed_of_sound [m/s]
temperature [K]
conditions.frames.
body.transform_to_inertial (rotation matrix)
inertial.velocity_vector [m/s]
conditions.propulsion.
throttle [-]
Outputs:
conditions.propulsion.outputs.
number_radial_stations [-]
number_azimuthal_stations [-]
disc_radial_distribution [m]
speed_of_sound [m/s]
density [kg/m-3]
velocity [m/s]
disc_tangential_induced_velocity [m/s]
disc_axial_induced_velocity [m/s]
disc_tangential_velocity [m/s]
disc_axial_velocity [m/s]
drag_coefficient [-]
lift_coefficient [-]
omega [rad/s]
disc_circulation [-]
blade_dQ_dR [N/m]
blade_dT_dr [N]
blade_thrust_distribution [N]
disc_thrust_distribution [N]
thrust_per_blade [N]
thrust_coefficient [-]
azimuthal_distribution [rad]
disc_azimuthal_distribution [rad]
blade_dQ_dR [N]
blade_dQ_dr [Nm]
blade_torque_distribution [Nm]
disc_torque_distribution [Nm]
torque_per_blade [Nm]
torque_coefficient [-]
power [W]
power_coefficient [-]
Properties Used:
self.
number_of_blades [-]
tip_radius [m]
twist_distribution [radians]
chord_distribution [m]
orientation_euler_angles [rad, rad, rad]
"""
# Unpack rotor blade parameters
B = self.number_of_blades
R = self.tip_radius
beta_0 = self.twist_distribution
c = self.chord_distribution
sweep = self.sweep_distribution # quarter chord distance from quarter chord of root airfoil
r_1d = self.radius_distribution
tc = self.thickness_to_chord
# Unpack rotor airfoil data
a_geo = self.airfoil_geometry
a_loc = self.airfoil_polar_stations
cl_sur = self.airfoil_cl_surrogates
cd_sur = self.airfoil_cd_surrogates
# Unpack rotor inputs and conditions
omega = self.inputs.omega
Na = self.number_azimuthal_stations
nonuniform_freestream = self.nonuniform_freestream
use_2d_analysis = self.use_2d_analysis
wake_method = self.wake_method
rotation = self.rotation
pitch_c = self.inputs.pitch_command
# Check for variable pitch
if np.any(pitch_c != 0) and not self.variable_pitch:
print(
"Warning: pitch commanded for a fixed-pitch rotor. Changing to variable pitch rotor for weights analysis."
)
self.variable_pitch = True
# Unpack freestream conditions
rho = conditions.freestream.density[:, 0, None]
mu = conditions.freestream.dynamic_viscosity[:, 0, None]
a = conditions.freestream.speed_of_sound[:, 0, None]
T = conditions.freestream.temperature[:, 0, None]
Vv = conditions.frames.inertial.velocity_vector
nu = mu / rho
rho_0 = rho
# Helpful shorthands
pi = np.pi
# Calculate total blade pitch
total_blade_pitch = beta_0 + pitch_c
# Velocity in the rotor frame
T_body2inertial = conditions.frames.body.transform_to_inertial
T_inertial2body = orientation_transpose(T_body2inertial)
V_body = orientation_product(T_inertial2body, Vv)
body2thrust = self.body_to_prop_vel()
T_body2thrust = orientation_transpose(
np.ones_like(T_body2inertial[:]) * body2thrust)
V_thrust = orientation_product(T_body2thrust, V_body)
# Check and correct for hover
V = V_thrust[:, 0, None]
V[V == 0.0] = 1E-6
# Number of radial stations and segment control points
Nr = len(c)
ctrl_pts = len(Vv)
# Non-dimensional radial distribution and differential radius
chi = r_1d / R
diff_r = np.diff(r_1d)
deltar = np.zeros(len(r_1d))
deltar[1:-1] = diff_r[0:-1] / 2 + diff_r[1:] / 2
deltar[0] = diff_r[0] / 2
deltar[-1] = diff_r[-1] / 2
# Calculating rotational parameters
omegar = np.outer(omega, r_1d)
n = omega / (2. * pi) # Rotations per second
# 2 dimensional radial distribution non dimensionalized
chi_2d = np.tile(chi[:, None], (1, Na))
chi_2d = np.repeat(chi_2d[None, :, :], ctrl_pts, axis=0)
r_dim_2d = np.tile(r_1d[:, None], (1, Na))
r_dim_2d = np.repeat(r_dim_2d[None, :, :], ctrl_pts, axis=0)
c_2d = np.tile(c[:, None], (1, Na))
c_2d = np.repeat(c_2d[None, :, :], ctrl_pts, axis=0)
# Azimuthal distribution of stations
psi = np.linspace(0, 2 * pi, Na + 1)[:-1]
psi_2d = np.tile(np.atleast_2d(psi), (Nr, 1))
psi_2d = np.repeat(psi_2d[None, :, :], ctrl_pts, axis=0)
# apply blade sweep to azimuthal position
if np.any(np.array([sweep]) != 0):
use_2d_analysis = True
sweep_2d = np.repeat(sweep[:, None], (1, Na))
sweep_offset_angles = np.tan(sweep_2d / r_dim_2d)
psi_2d += sweep_offset_angles
# Starting with uniform freestream
ua = 0
ut = 0
ur = 0
# Include velocities introduced by rotor incidence angles
if (np.any(abs(V_thrust[:, 1]) > 1e-3)
or np.any(abs(V_thrust[:, 2]) > 1e-3)) and use_2d_analysis:
# y-component of freestream in the propeller cartesian plane
Vy = V_thrust[:, 1, None, None]
Vy = np.repeat(Vy, Nr, axis=1)
Vy = np.repeat(Vy, Na, axis=2)
# z-component of freestream in the propeller cartesian plane
Vz = V_thrust[:, 2, None, None]
Vz = np.repeat(Vz, Nr, axis=1)
Vz = np.repeat(Vz, Na, axis=2)
# check for invalid rotation angle
if (rotation == 1) or (rotation == -1):
pass
else:
print("Invalid rotation direction. Setting to 1.")
rotation = 1
# compute resulting radial and tangential velocities in polar frame
utz = Vz * np.cos(psi_2d * rotation)
urz = Vz * np.sin(psi_2d * rotation)
uty = Vy * np.sin(psi_2d * rotation)
ury = Vy * np.cos(psi_2d * rotation)
ut += (utz + uty)
ur += (urz + ury)
ua += np.zeros_like(ut)
# Include external velocities introduced by user
if nonuniform_freestream:
use_2d_analysis = True
# include additional influences specified at rotor sections, shape=(ctrl_pts,Nr,Na)
ua += self.axial_velocities_2d
ut += self.tangential_velocities_2d
ur += self.radial_velocities_2d
if use_2d_analysis:
# make everything 2D with shape (ctrl_pts,Nr,Na)
size = (ctrl_pts, Nr, Na)
PSI = np.ones(size)
PSIold = np.zeros(size)
# 2-D freestream velocity and omega*r
V_2d = V_thrust[:, 0, None, None]
V_2d = np.repeat(V_2d, Na, axis=2)
V_2d = np.repeat(V_2d, Nr, axis=1)
omegar = (np.repeat(np.outer(omega, r_1d)[:, :, None], Na, axis=2))
# total velocities
Ua = V_2d + ua
# 2-D blade pitch and radial distributions
if np.size(pitch_c) > 1:
# control variable is the blade pitch, repeat around azimuth
beta = np.repeat(total_blade_pitch[:, :, None], Na, axis=2)
else:
beta = np.tile(total_blade_pitch[None, :, None],
(ctrl_pts, 1, Na))
r = np.tile(r_1d[None, :, None], (ctrl_pts, 1, Na))
c = np.tile(c[None, :, None], (ctrl_pts, 1, Na))
deltar = np.tile(deltar[None, :, None], (ctrl_pts, 1, Na))
# 2-D atmospheric properties
a = np.tile(np.atleast_2d(a), (1, Nr))
a = np.repeat(a[:, :, None], Na, axis=2)
nu = np.tile(np.atleast_2d(nu), (1, Nr))
nu = np.repeat(nu[:, :, None], Na, axis=2)
rho = np.tile(np.atleast_2d(rho), (1, Nr))
rho = np.repeat(rho[:, :, None], Na, axis=2)
T = np.tile(np.atleast_2d(T), (1, Nr))
T = np.repeat(T[:, :, None], Na, axis=2)
else:
# total velocities
r = r_1d
Ua = np.outer((V + ua), np.ones_like(r))
beta = total_blade_pitch
# Things that will change with iteration
size = (ctrl_pts, Nr)
PSI = np.ones(size)
PSIold = np.zeros(size)
# Total velocities
Ut = omegar - ut
U = np.sqrt(Ua * Ua + Ut * Ut + ur * ur)
if wake_method == 'momentum':
# Setup a Newton iteration
diff = 1.
tol = 1e-6 # Convergence tolerance
ii = 0
# BEMT Iteration
while (diff > tol):
# compute velocities
sin_psi = np.sin(PSI)
cos_psi = np.cos(PSI)
Wa = 0.5 * Ua + 0.5 * U * sin_psi
Wt = 0.5 * Ut + 0.5 * U * cos_psi
va = Wa - Ua
vt = Ut - Wt
# compute blade airfoil forces and properties
Cl, Cdval, alpha, Ma, W = compute_airfoil_aerodynamics(
beta, c, r, R, B, Wa, Wt, a, nu, a_loc, a_geo, cl_sur,
cd_sur, ctrl_pts, Nr, Na, tc, use_2d_analysis)
# compute inflow velocity and tip loss factor
lamdaw, F, piece = compute_inflow_and_tip_loss(r, R, Wa, Wt, B)
# compute Newton residual on circulation
Gamma = vt * (4. * pi * r / B) * F * (1. + (4. * lamdaw * R /
(pi * B * r)) *
(4. * lamdaw * R /
(pi * B * r)))**0.5
Rsquiggly = Gamma - 0.5 * W * c * Cl
# use analytical derivative to get dR_dpsi
dR_dpsi = compute_dR_dpsi(B, beta, r, R, Wt, Wa, U, Ut, Ua,
cos_psi, sin_psi, piece)
# update inflow angle
dpsi = -Rsquiggly / dR_dpsi
PSI = PSI + dpsi
diff = np.max(abs(PSIold - PSI))
PSIold = PSI
# If omega = 0, do not run BEMT convergence loop
if all(omega[:, 0]) == 0.:
break
# If its really not going to converge
if np.any(PSI > pi / 2) and np.any(dpsi > 0.0):
print("Rotor BEMT did not converge to a solution (Stall)")
break
ii += 1
if ii > 10000:
print(
"Rotor BEMT did not converge to a solution (Iteration Limit)"
)
break
elif wake_method == "helical_fixed_wake":
# converge on va for a semi-prescribed wake method
ii, ii_max = 0, 50
va_diff, tol = 1, 1e-3
while va_diff > tol:
# compute axial wake-induced velocity (a byproduct of the circulation distribution which is an input to the wake geometry)
va, vt = compute_HFW_inflow_velocities(self)
# compute new blade velocities
Wa = va + Ua
Wt = Ut - vt
# Compute aerodynamic forces based on specified input airfoil or surrogate
Cl, Cdval, alpha, Ma, W = compute_airfoil_aerodynamics(
beta, c, r, R, B, Wa, Wt, a, nu, a_loc, a_geo, cl_sur,
cd_sur, ctrl_pts, Nr, Na, tc, use_2d_analysis)
lamdaw, F, _ = compute_inflow_and_tip_loss(r, R, Wa, Wt, B)
va_diff = np.max(
abs(va - self.outputs.disc_axial_induced_velocity))
# compute HFW circulation at the blade
Gamma = 0.5 * W * c * Cl
# update the axial disc velocity based on new va from HFW
self.outputs.disc_axial_induced_velocity = self.outputs.disc_axial_induced_velocity + 0.5 * (
va - self.outputs.disc_axial_induced_velocity)
ii += 1
if ii > ii_max and va_diff > tol:
print(
"Semi-prescribed helical wake did not converge on axial inflow used for wake shape."
)
# tip loss correction for velocities, since tip loss correction is only applied to loads in prior BEMT iteration
va = F * va
vt = F * vt
lamdaw = r * (va + Ua) / (R * (Ut - vt))
# More Cd scaling from Mach from AA241ab notes for turbulent skin friction
Tw_Tinf = 1. + 1.78 * (Ma * Ma)
Tp_Tinf = 1. + 0.035 * (Ma * Ma) + 0.45 * (Tw_Tinf - 1.)
Tp = (Tp_Tinf) * T
Rp_Rinf = (Tp_Tinf**2.5) * (Tp + 110.4) / (T + 110.4)
Cd = ((1 / Tp_Tinf) * (1 / Rp_Rinf)**0.2) * Cdval
epsilon = Cd / Cl
epsilon[epsilon == np.inf] = 10.
# thrust and torque and their derivatives on the blade.
blade_T_distribution = rho * (Gamma * (Wt - epsilon * Wa)) * deltar
blade_Q_distribution = rho * (Gamma * (Wa + epsilon * Wt) * r) * deltar
blade_dT_dr = rho * (Gamma * (Wt - epsilon * Wa))
blade_dQ_dr = rho * (Gamma * (Wa + epsilon * Wt) * r)
if use_2d_analysis:
blade_T_distribution_2d = blade_T_distribution
blade_Q_distribution_2d = blade_Q_distribution
blade_dT_dr_2d = blade_dT_dr
blade_dQ_dr_2d = blade_dQ_dr
blade_Gamma_2d = Gamma
alpha_2d = alpha
Va_2d = Wa
Vt_2d = Wt
Va_avg = np.average(Wa, axis=2) # averaged around the azimuth
Vt_avg = np.average(Wt, axis=2) # averaged around the azimuth
Va_ind_2d = va
Vt_ind_2d = vt
Vt_ind_avg = np.average(vt, axis=2)
Va_ind_avg = np.average(va, axis=2)
# set 1d blade loadings to be the average:
blade_T_distribution = np.mean((blade_T_distribution_2d), axis=2)
blade_Q_distribution = np.mean((blade_Q_distribution_2d), axis=2)
blade_dT_dr = np.mean((blade_dT_dr_2d), axis=2)
blade_dQ_dr = np.mean((blade_dQ_dr_2d), axis=2)
# compute the hub force / rotor drag distribution along the blade
dL_2d = 0.5 * rho * c_2d * Cd * omegar**2 * deltar
dD_2d = 0.5 * rho * c_2d * Cl * omegar**2 * deltar
rotor_drag_distribution = np.mean(dL_2d * np.sin(psi_2d) +
dD_2d * np.cos(psi_2d),
axis=2)
else:
Va_2d = np.repeat(Wa[:, :, None], Na, axis=2)
Vt_2d = np.repeat(Wt[:, :, None], Na, axis=2)
blade_T_distribution_2d = np.repeat(blade_T_distribution[:, :,
None],
Na,
axis=2)
blade_Q_distribution_2d = np.repeat(blade_Q_distribution[:, :,
None],
Na,
axis=2)
blade_dT_dr_2d = np.repeat(blade_dT_dr[:, :, None], Na, axis=2)
blade_dQ_dr_2d = np.repeat(blade_dQ_dr[:, :, None], Na, axis=2)
blade_Gamma_2d = np.repeat(Gamma[:, :, None], Na, axis=2)
alpha_2d = np.repeat(alpha[:, :, None], Na, axis=2)
Vt_avg = Wt
Va_avg = Wa
Vt_ind_avg = vt
Va_ind_avg = va
Va_ind_2d = np.repeat(va[:, :, None], Na, axis=2)
Vt_ind_2d = np.repeat(vt[:, :, None], Na, axis=2)
# compute the hub force / rotor drag distribution along the blade
dL = 0.5 * rho * c * Cd * omegar**2 * deltar
dL_2d = np.repeat(dL[:, :, None], Na, axis=2)
dD = 0.5 * rho * c * Cl * omegar**2 * deltar
dD_2d = np.repeat(dD[:, :, None], Na, axis=2)
rotor_drag_distribution = np.mean(dL_2d * np.sin(psi_2d) +
dD_2d * np.cos(psi_2d),
axis=2)
# forces
thrust = np.atleast_2d((B * np.sum(blade_T_distribution, axis=1))).T
torque = np.atleast_2d((B * np.sum(blade_Q_distribution, axis=1))).T
rotor_drag = np.atleast_2d(
(B * np.sum(rotor_drag_distribution, axis=1))).T
power = omega * torque
# calculate coefficients
D = 2 * R
Cq = torque / (rho_0 * (n * n) * (D * D * D * D * D))
Ct = thrust / (rho_0 * (n * n) * (D * D * D * D))
Cp = power / (rho_0 * (n * n * n) * (D * D * D * D * D))
Crd = rotor_drag / (rho_0 * (n * n) * (D * D * D * D))
etap = V * thrust / power
# prevent things from breaking
Cq[Cq < 0] = 0.
Ct[Ct < 0] = 0.
Cp[Cp < 0] = 0.
thrust[conditions.propulsion.throttle[:, 0] <= 0.0] = 0.0
power[conditions.propulsion.throttle[:, 0] <= 0.0] = 0.0
torque[conditions.propulsion.throttle[:, 0] <= 0.0] = 0.0
rotor_drag[conditions.propulsion.throttle[:, 0] <= 0.0] = 0.0
thrust[omega < 0.0] = -thrust[omega < 0.0]
thrust[omega == 0.0] = 0.0
power[omega == 0.0] = 0.0
torque[omega == 0.0] = 0.0
rotor_drag[omega == 0.0] = 0.0
Ct[omega == 0.0] = 0.0
Cp[omega == 0.0] = 0.0
etap[omega == 0.0] = 0.0
# Make the thrust a 3D vector
thrust_prop_frame = np.zeros((ctrl_pts, 3))
thrust_prop_frame[:, 0] = thrust[:, 0]
thrust_vector = orientation_product(
orientation_transpose(T_body2thrust), thrust_prop_frame)
# Assign efficiency to network
conditions.propulsion.etap = etap
# Store data
self.azimuthal_distribution = psi
results_conditions = Data
outputs = results_conditions(
number_radial_stations=Nr,
number_azimuthal_stations=Na,
disc_radial_distribution=r_dim_2d,
speed_of_sound=conditions.freestream.speed_of_sound,
density=conditions.freestream.density,
velocity=Vv,
blade_tangential_induced_velocity=Vt_ind_avg,
blade_axial_induced_velocity=Va_ind_avg,
blade_tangential_velocity=Vt_avg,
blade_axial_velocity=Va_avg,
disc_tangential_induced_velocity=Vt_ind_2d,
disc_axial_induced_velocity=Va_ind_2d,
disc_tangential_velocity=Vt_2d,
disc_axial_velocity=Va_2d,
drag_coefficient=Cd,
lift_coefficient=Cl,
omega=omega,
disc_circulation=blade_Gamma_2d,
blade_dT_dr=blade_dT_dr,
disc_dT_dr=blade_dT_dr_2d,
blade_thrust_distribution=blade_T_distribution,
disc_thrust_distribution=blade_T_distribution_2d,
disc_effective_angle_of_attack=alpha_2d,
thrust_per_blade=thrust / B,
thrust_coefficient=Ct,
disc_azimuthal_distribution=psi_2d,
blade_dQ_dr=blade_dQ_dr,
disc_dQ_dr=blade_dQ_dr_2d,
blade_torque_distribution=blade_Q_distribution,
disc_torque_distribution=blade_Q_distribution_2d,
torque_per_blade=torque / B,
torque_coefficient=Cq,
power=power,
power_coefficient=Cp,
converged_inflow_ratio=lamdaw,
propeller_efficiency=etap,
blade_H_distribution=rotor_drag_distribution,
rotor_drag=rotor_drag,
rotor_drag_coefficient=Crd,
)
return thrust_vector, torque, power, Cp, outputs, etap
def update_orientations(segment,state):
""" Updates the orientation of the vehicle throughout the mission for each relevant axis
Assumptions:
This assumes the vehicle has 3 frames: inertial, body, and wind. There also contains bits for stability axis which are not used. Creates tensors and solves for alpha and beta.
Inputs:
state.conditions:
frames.inertial.velocity_vector [meters/second]
frames.body.inertial_rotations [Radians]
segment.analyses.planet.features.mean_radius [meters]
state.numerics.time.integrate [float]
Outputs:
state.conditions:
aerodynamics.angle_of_attack [Radians]
aerodynamics.side_slip_angle [Radians]
aerodynamics.roll_angle [Radians]
frames.body.transform_to_inertial [Radians]
frames.wind.body_rotations [Radians]
frames.wind.transform_to_inertial [Radians]
Properties Used:
N/A
"""
# unpack
conditions = state.conditions
V_inertial = conditions.frames.inertial.velocity_vector
body_inertial_rotations = conditions.frames.body.inertial_rotations
# ------------------------------------------------------------------
# Body Frame
# ------------------------------------------------------------------
# body frame rotations
phi = body_inertial_rotations[:,0,None]
theta = body_inertial_rotations[:,1,None]
psi = body_inertial_rotations[:,2,None]
# body frame tranformation matrices
T_inertial2body = angles_to_dcms(body_inertial_rotations,(2,1,0))
T_body2inertial = orientation_transpose(T_inertial2body)
# transform inertial velocity to body frame
V_body = orientation_product(T_inertial2body,V_inertial)
# project inertial velocity into body x-z plane
V_stability = V_body
V_stability[:,1] = 0
V_stability_magnitude = np.sqrt( np.sum(V_stability**2,axis=1) )[:,None]
#V_stability_direction = V_stability / V_stability_magnitude
# calculate angle of attack
alpha = np.arctan2(V_stability[:,2],V_stability[:,0])[:,None]
# calculate side slip
beta = np.arctan2(V_body[:,1],V_stability_magnitude[:,0])[:,None]
# pack aerodynamics angles
conditions.aerodynamics.angle_of_attack[:,0] = alpha[:,0]
conditions.aerodynamics.side_slip_angle[:,0] = beta[:,0]
conditions.aerodynamics.roll_angle[:,0] = phi[:,0]
# pack transformation tensor
conditions.frames.body.transform_to_inertial = T_body2inertial
# ------------------------------------------------------------------
# Wind Frame
# ------------------------------------------------------------------
# back calculate wind frame rotations
wind_body_rotations = body_inertial_rotations * 0.
wind_body_rotations[:,0] = 0 # no roll in wind frame
wind_body_rotations[:,1] = alpha[:,0] # theta is angle of attack
wind_body_rotations[:,2] = beta[:,0] # psi is side slip angle
# wind frame tranformation matricies
T_wind2body = angles_to_dcms(wind_body_rotations,(2,1,0))
T_body2wind = orientation_transpose(T_wind2body)
T_wind2inertial = orientation_product(T_wind2body,T_body2inertial)
# pack wind rotations
conditions.frames.wind.body_rotations = wind_body_rotations
# pack transformation tensor
conditions.frames.wind.transform_to_inertial = T_wind2inertial
return
def plot_vehicle(vehicle,
save_figure=False,
plot_control_points=True,
save_filename="Vehicle_Geometry"):
"""This plots vortex lattice panels created when Fidelity Zero Aerodynamics
Routine is initialized
Assumptions:
None
Source:
None
Inputs:
vehicle
Outputs:
Plots
Properties Used:
N/A
"""
# unpack vortex distribution
VD = vehicle.vortex_distribution
face_color = 'grey'
edge_color = 'grey'
alpha_val = 0.5
# initalize figure
fig = plt.figure(save_filename)
fig.set_size_inches(8, 8)
axes = Axes3D(fig)
axes.view_init(elev=30, azim=210)
n_cp = VD.n_cp
for i in range(n_cp):
X = [VD.XA1[i], VD.XB1[i], VD.XB2[i], VD.XA2[i]]
Y = [VD.YA1[i], VD.YB1[i], VD.YB2[i], VD.YA2[i]]
Z = [VD.ZA1[i], VD.ZB1[i], VD.ZB2[i], VD.ZA2[i]]
verts = [list(zip(X, Y, Z))]
collection = Poly3DCollection(verts)
collection.set_facecolor(face_color)
collection.set_edgecolor(edge_color)
collection.set_alpha(alpha_val)
axes.add_collection3d(collection)
max_range = np.array([
VD.X.max() - VD.X.min(),
VD.Y.max() - VD.Y.min(),
VD.Z.max() - VD.Z.min()
]).max() / 2.0
mid_x = (VD.X.max() + VD.X.min()) * 0.5
mid_y = (VD.Y.max() + VD.Y.min()) * 0.5
mid_z = (VD.Z.max() + VD.Z.min()) * 0.5
axes.set_xlim(mid_x - max_range, mid_x + max_range)
axes.set_ylim(mid_y - max_range, mid_y + max_range)
axes.set_zlim(mid_z - max_range, mid_z + max_range)
if plot_control_points:
axes.scatter(VD.XC, VD.YC, VD.ZC, c='r', marker='o')
if 'Wake' in VD:
face_color = 'white'
edge_color = 'blue'
alpha = 0.5
num_prop = len(VD.Wake.XA1[:, 0, 0, 0])
nts = len(VD.Wake.XA1[0, :, 0, 0])
num_B = len(VD.Wake.XA1[0, 0, :, 0])
dim_R = len(VD.Wake.XA1[0, 0, 0, :])
for p_idx in range(num_prop):
for t_idx in range(nts):
for B_idx in range(num_B):
for loc in range(dim_R):
X = [
VD.Wake.XA1[p_idx, t_idx, B_idx, loc],
VD.Wake.XB1[p_idx, t_idx, B_idx, loc],
VD.Wake.XB2[p_idx, t_idx, B_idx,
loc], VD.Wake.XA2[p_idx, t_idx, B_idx,
loc]
]
Y = [
VD.Wake.YA1[p_idx, t_idx, B_idx, loc],
VD.Wake.YB1[p_idx, t_idx, B_idx, loc],
VD.Wake.YB2[p_idx, t_idx, B_idx,
loc], VD.Wake.YA2[p_idx, t_idx, B_idx,
loc]
]
Z = [
VD.Wake.ZA1[p_idx, t_idx, B_idx, loc],
VD.Wake.ZB1[p_idx, t_idx, B_idx, loc],
VD.Wake.ZB2[p_idx, t_idx, B_idx,
loc], VD.Wake.ZA2[p_idx, t_idx, B_idx,
loc]
]
verts = [list(zip(X, Y, Z))]
collection = Poly3DCollection(verts)
collection.set_facecolor(face_color)
collection.set_edgecolor(edge_color)
collection.set_alpha(alpha)
axes.add_collection3d(collection)
if np.all(VD.FUS_SURF_PTS) != None:
face_color = 'grey'
edge_color = 'black'
alpha = 1
num_fus_segs = len(VD.FUS_SURF_PTS[:, 0, 0])
tesselation = len(VD.FUS_SURF_PTS[0, :, 0])
for i_seg in range(num_fus_segs - 1):
for i_tes in range(tesselation - 1):
X = [
VD.FUS_SURF_PTS[i_seg, i_tes,
0], VD.FUS_SURF_PTS[i_seg, i_tes + 1, 0],
VD.FUS_SURF_PTS[i_seg + 1, i_tes + 1,
0], VD.FUS_SURF_PTS[i_seg + 1, i_tes, 0]
]
Y = [
VD.FUS_SURF_PTS[i_seg, i_tes,
1], VD.FUS_SURF_PTS[i_seg, i_tes + 1, 1],
VD.FUS_SURF_PTS[i_seg + 1, i_tes + 1,
1], VD.FUS_SURF_PTS[i_seg + 1, i_tes, 1]
]
Z = [
VD.FUS_SURF_PTS[i_seg, i_tes,
2], VD.FUS_SURF_PTS[i_seg, i_tes + 1, 2],
VD.FUS_SURF_PTS[i_seg + 1, i_tes + 1,
2], VD.FUS_SURF_PTS[i_seg + 1, i_tes, 2]
]
verts = [list(zip(X, Y, Z))]
collection = Poly3DCollection(verts)
collection.set_facecolor(face_color)
collection.set_edgecolor(edge_color)
collection.set_alpha(alpha)
axes.add_collection3d(collection)
for propulsor in vehicle.propulsors:
if ('propeller' in propulsor.keys()) or ('rotor' in propulsor.keys()):
try:
prop = propulsor.propeller
except:
prop = propulsor.rotor
# ------------------------------------------------------------------------
# Generate Propeller Geoemtry
# ------------------------------------------------------------------------
# unpack
Rt = prop.tip_radius
Rh = prop.hub_radius
num_B = prop.number_blades
a_sec = prop.airfoil_geometry
a_secl = prop.airfoil_polar_stations
beta = prop.twist_distribution
b = prop.chord_distribution
r = prop.radius_distribution
MCA = prop.mid_chord_aligment
t = prop.max_thickness_distribution
ta = -propulsor.thrust_angle
n_points = 10
af_pts = (2 * n_points) - 1
dim = len(b)
num_props = len(prop.origin)
theta = np.linspace(0, 2 * np.pi, num_B + 1)[:-1]
# create empty arrays for storing geometry
G = Data()
G.XA1 = np.zeros((dim - 1, af_pts))
G.YA1 = np.zeros_like(G.XA1)
G.ZA1 = np.zeros_like(G.XA1)
G.XA2 = np.zeros_like(G.XA1)
G.YA2 = np.zeros_like(G.XA1)
G.ZA2 = np.zeros_like(G.XA1)
G.XB1 = np.zeros_like(G.XA1)
G.YB1 = np.zeros_like(G.XA1)
G.ZB1 = np.zeros_like(G.XA1)
G.XB2 = np.zeros_like(G.XA1)
G.YB2 = np.zeros_like(G.XA1)
G.ZB2 = np.zeros_like(G.XA1)
for n_p in range(num_props):
rot = prop.rotation[n_p]
a_o = 0
flip_1 = (np.pi / 2)
flip_2 = (np.pi / 2)
for i in range(num_B):
# get airfoil coordinate geometry
airfoil_data = import_airfoil_geometry(a_sec,
npoints=n_points)
# store points of airfoil in similar format as Vortex Points (i.e. in vertices)
for j in range(dim -
1): # loop through each radial station
# --------------------------------------------
# INNER SECTION
# --------------------------------------------
# INNER SECTION POINTS
ixpts = airfoil_data.x_coordinates[a_secl[j]]
izpts = airfoil_data.y_coordinates[a_secl[j]]
iba_max_t = airfoil_data.thickness_to_chord[a_secl[j]]
iba_xp = rot * (-MCA[j] + ixpts * b[j]
) # x coord of airfoil
iba_yp = r[j] * np.ones_like(iba_xp) # radial location
iba_zp = izpts * (t[j] / iba_max_t
) # former airfoil y coord
iba_matrix = np.zeros((len(iba_zp), 3))
iba_matrix[:, 0] = iba_xp
iba_matrix[:, 1] = iba_yp
iba_matrix[:, 2] = iba_zp
# ROTATION MATRICES FOR INNER SECTION
# rotation about y axis to create twist and position blade upright
iba_trans_1 = [[
np.cos(rot * flip_1 - rot * beta[j]), 0,
-np.sin(rot * flip_1 - rot * beta[j])
], [0, 1, 0],
[
np.sin(rot * flip_1 -
rot * beta[j]), 0,
np.cos(rot * flip_1 - rot * beta[j])
]]
# rotation about x axis to create azimuth locations
iba_trans_2 = [
[1, 0, 0],
[
0,
np.cos(theta[i] + rot * a_o + flip_2),
np.sin(theta[i] + rot * a_o + flip_2)
],
[
0,
np.sin(theta[i] + rot * a_o + flip_2),
np.cos(theta[i] + rot * a_o + flip_2)
]
]
# roation about y to orient propeller/rotor to thrust angle
iba_trans_3 = [[np.cos(ta), 0, -np.sin(ta)], [0, 1, 0],
[np.sin(ta), 0,
np.cos(ta)]]
iba_trans = np.matmul(
iba_trans_3, np.matmul(iba_trans_2, iba_trans_1))
irot_mat = np.repeat(iba_trans[np.newaxis, :, :],
len(iba_yp),
axis=0)
# --------------------------------------------
# OUTER SECTION
# --------------------------------------------
# OUTER SECTION POINTS
oxpts = airfoil_data.x_coordinates[a_secl[j + 1]]
ozpts = airfoil_data.y_coordinates[a_secl[j + 1]]
oba_max_t = airfoil_data.thickness_to_chord[a_secl[j +
1]]
oba_xp = -MCA[j + 1] + oxpts * b[
j + 1] # x coord of airfoil
oba_yp = r[j + 1] * np.ones_like(
oba_xp) # radial location
oba_zp = ozpts * (t[j + 1] / oba_max_t
) # former airfoil y coord
oba_matrix = np.zeros((len(oba_zp), 3))
oba_matrix[:, 0] = oba_xp
oba_matrix[:, 1] = oba_yp
oba_matrix[:, 2] = oba_zp
# ROTATION MATRICES FOR OUTER SECTION
# rotation about y axis to create twist and position blade upright
oba_trans_1 = [
[
np.cos(rot * flip_1 - rot * beta[j + 1]), 0,
-np.sin(rot * flip_1 - rot * beta[j + 1])
], [0, 1, 0],
[
np.sin(rot * flip_1 - rot * beta[j + 1]), 0,
np.cos(rot * flip_1 - rot * beta[j + 1])
]
]
# rotation about x axis to create azimuth locations
oba_trans_2 = [
[1, 0, 0],
[
0,
np.cos(theta[i] + rot * a_o + flip_2),
np.sin(theta[i] + rot * a_o + flip_2)
],
[
0,
np.sin(theta[i] + rot * a_o + flip_2),
np.cos(theta[i] + rot * a_o + flip_2)
]
]
# roation about y to orient propeller/rotor to thrust angle
oba_trans_3 = [[np.cos(ta), 0, -np.sin(ta)], [0, 1, 0],
[np.sin(ta), 0,
np.cos(ta)]]
oba_trans = np.matmul(
oba_trans_3, np.matmul(oba_trans_2, oba_trans_1))
orot_mat = np.repeat(oba_trans[np.newaxis, :, :],
len(oba_yp),
axis=0)
# ---------------------------------------------------------------------------------------------
# ROTATE POINTS
iba_mat = orientation_product(irot_mat, iba_matrix)
oba_mat = orientation_product(orot_mat, oba_matrix)
# ---------------------------------------------------------------------------------------------
# store points
G.XA1[j, :] = iba_mat[:-1, 0] + prop.origin[n_p][0]
G.YA1[j, :] = iba_mat[:-1, 1] + prop.origin[n_p][1]
G.ZA1[j, :] = iba_mat[:-1, 2] + prop.origin[n_p][2]
G.XA2[j, :] = iba_mat[1:, 0] + prop.origin[n_p][0]
G.YA2[j, :] = iba_mat[1:, 1] + prop.origin[n_p][1]
G.ZA2[j, :] = iba_mat[1:, 2] + prop.origin[n_p][2]
G.XB1[j, :] = oba_mat[:-1, 0] + prop.origin[n_p][0]
G.YB1[j, :] = oba_mat[:-1, 1] + prop.origin[n_p][1]
G.ZB1[j, :] = oba_mat[:-1, 2] + prop.origin[n_p][2]
G.XB2[j, :] = oba_mat[1:, 0] + prop.origin[n_p][0]
G.YB2[j, :] = oba_mat[1:, 1] + prop.origin[n_p][1]
G.ZB2[j, :] = oba_mat[1:, 2] + prop.origin[n_p][2]
# ------------------------------------------------------------------------
# Plot Propeller Blade
# ------------------------------------------------------------------------
prop_face_color = 'red'
prop_edge_color = 'red'
prop_alpha = 1
for sec in range(dim - 1):
for loc in range(af_pts):
X = [
G.XA1[sec, loc], G.XB1[sec, loc],
G.XB2[sec, loc], G.XA2[sec, loc]
]
Y = [
G.YA1[sec, loc], G.YB1[sec, loc],
G.YB2[sec, loc], G.YA2[sec, loc]
]
Z = [
G.ZA1[sec, loc], G.ZB1[sec, loc],
G.ZB2[sec, loc], G.ZA2[sec, loc]
]
prop_verts = [list(zip(X, Y, Z))]
prop_collection = Poly3DCollection(prop_verts)
prop_collection.set_facecolor(prop_face_color)
prop_collection.set_edgecolor(prop_edge_color)
prop_collection.set_alpha(prop_alpha)
axes.add_collection3d(prop_collection)
plt.axis('off')
plt.grid(None)
return
def update_orientations(segment,state):
# unpack
conditions = state.conditions
V_inertial = conditions.frames.inertial.velocity_vector
body_inertial_rotations = conditions.frames.body.inertial_rotations
# ------------------------------------------------------------------
# Body Frame
# ------------------------------------------------------------------
# body frame rotations
phi = body_inertial_rotations[:,0,None]
theta = body_inertial_rotations[:,1,None]
psi = body_inertial_rotations[:,2,None]
# body frame tranformation matrices
T_inertial2body = angles_to_dcms(body_inertial_rotations,(2,1,0))
T_body2inertial = orientation_transpose(T_inertial2body)
# transform inertial velocity to body frame
V_body = orientation_product(T_inertial2body,V_inertial)
# project inertial velocity into body x-z plane
V_stability = V_body
V_stability[:,1] = 0
V_stability_magnitude = np.sqrt( np.sum(V_stability**2,axis=1) )[:,None]
#V_stability_direction = V_stability / V_stability_magnitude
# calculate angle of attack
alpha = np.arctan2(V_stability[:,2],V_stability[:,0])[:,None]
# calculate side slip
beta = np.arctan2(V_body[:,1],V_stability_magnitude[:,0])[:,None]
# pack aerodynamics angles
conditions.aerodynamics.angle_of_attack[:,0] = alpha[:,0]
conditions.aerodynamics.side_slip_angle[:,0] = beta[:,0]
conditions.aerodynamics.roll_angle[:,0] = phi[:,0]
# pack transformation tensor
conditions.frames.body.transform_to_inertial = T_body2inertial
# ------------------------------------------------------------------
# Wind Frame
# ------------------------------------------------------------------
# back calculate wind frame rotations
wind_body_rotations = body_inertial_rotations * 0.
wind_body_rotations[:,0] = 0 # no roll in wind frame
wind_body_rotations[:,1] = alpha[:,0] # theta is angle of attack
wind_body_rotations[:,2] = beta[:,0] # psi is side slip angle
# wind frame tranformation matricies
T_wind2body = angles_to_dcms(wind_body_rotations,(2,1,0))
T_body2wind = orientation_transpose(T_wind2body)
T_wind2inertial = orientation_product(T_wind2body,T_body2inertial)
# pack wind rotations
conditions.frames.wind.body_rotations = wind_body_rotations
# pack transformation tensor
conditions.frames.wind.transform_to_inertial = T_wind2inertial
return
def compute_propeller_nonuniform_freestream(prop, upstream_wake, conditions):
""" Computes the inflow velocities in the frame of the rotating propeller
Inputs:
prop. SUAVE propeller
tip_radius - propeller radius [m]
rotation - propeller rotation direction [-]
thrust_angle - thrust angle of prop [rad]
number_radial_stations - number of propeller radial stations [-]
number_azimuthal_stations - number of propeller azimuthal stations [-]
upstream_wake.
u_velocities - Streamwise velocities from upstream wake
v_velocities - Spanwise velocities from upstream wake
w_velocities - Downwash velocities from upstream wake
VD - Vortex distribution from upstream wake
conditions.
frames
Outputs:
Va Axial velocities at propeller [m/s]
Vt Tangential velocities at propeller [m/s]
Vr Radial velocities at propeller [m/s]
"""
# unpack propeller parameters
Vv = conditions.frames.inertial.velocity_vector
R = prop.tip_radius
rotation = prop.rotation
theta = prop.thrust_angle
c = prop.chord_distribution
Na = prop.number_azimuthal_stations
Nr = len(c)
ua_wing = upstream_wake.u_velocities
uv_wing = upstream_wake.v_velocities
uw_wing = upstream_wake.w_velocities
VD = upstream_wake.VD
# Velocity in the Body frame
T_body2inertial = conditions.frames.body.transform_to_inertial
T_inertial2body = orientation_transpose(T_body2inertial)
V_body = orientation_product(T_inertial2body, Vv)
body2thrust = np.array([[np.cos(theta), 0.,
np.sin(theta)], [0., 1., 0.],
[-np.sin(theta), 0.,
np.cos(theta)]])
T_body2thrust = orientation_transpose(
np.ones_like(T_body2inertial[:]) * body2thrust)
V_thrust = orientation_product(T_body2thrust, V_body)
# azimuth distribution
psi = np.linspace(0, 2 * np.pi, Na + 1)[:-1]
psi_2d = np.tile(np.atleast_2d(psi).T, (1, Nr))
# 2 dimensiona radial distribution non dimensionalized
chi = prop.radius_distribution / R
# Reframe the wing induced velocities:
y_center = prop.origin[0][1]
# New points to interpolate data: (corresponding to r,phi locations on propeller disc)
points = np.array([[VD.YC[i], VD.ZC[i]] for i in range(len(VD.YC))])
ycoords = np.reshape(R * chi * np.cos(psi_2d), (Nr * Na, ))
zcoords = prop.origin[0][2] + np.reshape(R * chi * np.sin(psi_2d),
(Nr * Na, ))
xi = np.array([[y_center + ycoords[i], zcoords[i]]
for i in range(len(ycoords))])
ua_w = sp.interpolate.griddata(points, ua_wing, xi, method='linear')
uv_w = sp.interpolate.griddata(points, uv_wing, xi, method='linear')
uw_w = sp.interpolate.griddata(points, uw_wing, xi, method='linear')
ua_wing = np.reshape(ua_w, (Na, Nr))
uw_wing = np.reshape(uw_w, (Na, Nr))
uv_wing = np.reshape(uv_w, (Na, Nr))
if rotation == [1]:
Vt_2d = V_thrust[:, 0] * (
-np.array(uw_wing) * np.cos(psi_2d) +
np.array(uv_wing) * np.sin(psi_2d)
) # velocity tangential to the disk plane, positive toward the trailing edge eqn 6.34 pg 165
Vr_2d = V_thrust[:, 0] * (-np.array(uw_wing) * np.sin(psi_2d) -
np.array(uv_wing) * np.cos(psi_2d)
) # radial velocity , positive outward
Va_2d = V_thrust[:, 0] * np.array(
ua_wing
) # velocity perpendicular to the disk plane, positive downward eqn 6.36 pg 166
else:
Vt_2d = V_thrust[:, 0] * (
np.array(uw_wing) * np.cos(psi_2d) -
np.array(uv_wing) * np.sin(psi_2d)
) # velocity tangential to the disk plane, positive toward the trailing edge
Vr_2d = V_thrust[:, 0] * (-np.array(uw_wing) * np.sin(psi_2d) -
np.array(uv_wing) * np.cos(psi_2d)
) # radial velocity , positive outward
Va_2d = V_thrust[:, 0] * np.array(
ua_wing
) # velocity perpendicular to the disk plane, positive downward
# Append velocities to propeller
prop.tangential_velocities_2d = Vt_2d
prop.radial_velocities_2d = Vr_2d
prop.axial_velocities_2d = Va_2d
return prop
def spin(self,conditions):
"""Analyzes a propeller given geometry and operating conditions.
Assumptions:
per source
Source:
Qprop theory document
Inputs:
self.inputs.omega [radian/s]
conditions.freestream.
density [kg/m^3]
dynamic_viscosity [kg/(m-s)]
speed_of_sound [m/s]
temperature [K]
conditions.frames.
body.transform_to_inertial (rotation matrix)
inertial.velocity_vector [m/s]
conditions.propulsion.
throttle [-]
Outputs:
conditions.propulsion.acoustic_outputs.
number_sections [-]
r0 [m]
airfoil_chord [m]
blades_number [-]
propeller_diameter [m]
drag_coefficient [-]
lift_coefficient [-]
omega [radian/s]
velocity [m/s]
thrust [N]
power [W]
mid_chord_aligment [m] (distance from the mid chord to the line axis out of the center of the blade)
conditions.propulsion.etap [-]
thrust [N]
torque [Nm]
power [W]
Cp [-] (coefficient of power)
Properties Used:
self.prop_attributes.
number_blades [-]
tip_radius [m]
hub_radius [m]
twist_distribution [radians]
chord_distribution [m]
mid_chord_aligment [m] (distance from the mid chord to the line axis out of the center of the blade)
self.thrust_angle [radians]
"""
#Unpack
B = self.prop_attributes.number_blades
R = self.prop_attributes.tip_radius
Rh = self.prop_attributes.hub_radius
beta = self.prop_attributes.twist_distribution
c = self.prop_attributes.chord_distribution
omega1 = self.inputs.omega
rho = conditions.freestream.density[:,0,None]
mu = conditions.freestream.dynamic_viscosity[:,0,None]
Vv = conditions.frames.inertial.velocity_vector
a = conditions.freestream.speed_of_sound[:,0,None]
T = conditions.freestream.temperature[:,0,None]
theta = self.thrust_angle
BB = B*B
BBB = BB*B
# Velocity in the Body frame
T_body2inertial = conditions.frames.body.transform_to_inertial
T_inertial2body = orientation_transpose(T_body2inertial)
V_body = orientation_product(T_inertial2body,Vv)
# Velocity transformed to the propulsor frame
body2thrust = np.array([[np.cos(theta), 0., np.sin(theta)],[0., 1., 0.], [-np.sin(theta), 0., np.cos(theta)]])
T_body2thrust = orientation_transpose(np.ones_like(T_body2inertial[:])*body2thrust)
V_thrust = orientation_product(T_body2thrust,V_body)
# Now just use the aligned velocity
V = V_thrust[:,0,None]
nu = mu/rho
tol = 1e-5 # Convergence tolerance
omega = omega1*1.0
omega = np.abs(omega)
######
# Enter airfoil data in a better way, there is currently Re and Ma scaling from DAE51 data
######
#Things that don't change with iteration
N = len(c) # Number of stations
chi0 = Rh/R # Where the propeller blade actually starts
chi = np.linspace(chi0,1,N+1) # Vector of nondimensional radii
chi = chi[0:N]
lamda = V/(omega*R) # Speed ratio
r = chi*R # Radial coordinate
pi = np.pi
pi2 = pi*pi
x = r*np.multiply(omega,1/V) # Nondimensional distance
n = omega/(2.*pi) # Cycles per second
J = V/(2.*R*n)
sigma = np.multiply(B*c,1./(2.*pi*r))
#I make the assumption that externally-induced velocity at the disk is zero
#This can be easily changed if needed in the future:
ua = 0.0
ut = 0.0
omegar = np.outer(omega,r)
Ua = np.outer((V + ua),np.ones_like(r))
Ut = omegar - ut
U = np.sqrt(Ua*Ua + Ut*Ut)
#Things that will change with iteration
size = (len(a),N)
#Setup a Newton iteration
psi = np.ones(size)
psiold = np.zeros(size)
diff = 1.
ii = 0
while (diff>tol):
sin_psi = np.sin(psi)
cos_psi = np.cos(psi)
Wa = 0.5*Ua + 0.5*U*sin_psi
Wt = 0.5*Ut + 0.5*U*cos_psi
#va = Wa - Ua
vt = Ut - Wt
alpha = beta - np.arctan2(Wa,Wt)
W = (Wa*Wa + Wt*Wt)**0.5
Ma = (W)/a #a is the speed of sound
#if np.any(Ma> 1.0):
#warn('Propeller blade tips are supersonic.', Warning)
lamdaw = r*Wa/(R*Wt)
# Limiter to keep from Nan-ing
lamdaw[lamdaw<0.] = 0.
f = (B/2.)*(1.-r/R)/lamdaw
piece = np.exp(-f)
arccos_piece = np.arccos(piece)
F = 2.*arccos_piece/pi
Gamma = vt*(4.*pi*r/B)*F*(1.+(4.*lamdaw*R/(pi*B*r))*(4.*lamdaw*R/(pi*B*r)))**0.5
# Ok, from the airfoil data, given Re, Ma, alpha we need to find Cl
Cl = 2.*pi*alpha
# By 90 deg, it's totally stalled.
Cl[alpha>=pi/2] = 0.
# Scale for Mach, this is Karmen_Tsien
Cl[Ma[:,:]<1.] = Cl[Ma[:,:]<1.]/((1-Ma[Ma[:,:]<1.]*Ma[Ma[:,:]<1.])**0.5+((Ma[Ma[:,:]<1.]*Ma[Ma[:,:]<1.])/(1+(1-Ma[Ma[:,:]<1.]*Ma[Ma[:,:]<1.])**0.5))*Cl[Ma<1.]/2)
# If the blade segments are supersonic, don't scale
Cl[Ma[:,:]>=1.] = Cl[Ma[:,:]>=1.]
Rsquiggly = Gamma - 0.5*W*c*Cl
#An analytical derivative for dR_dpsi, this is derived by taking a derivative of the above equations
#This was solved symbolically in Matlab and exported
f_wt_2 = 4*Wt*Wt
f_wa_2 = 4*Wa*Wa
Ucospsi = U*cos_psi
Usinpsi = U*sin_psi
Utcospsi = Ut*cos_psi
Uasinpsi = Ua*sin_psi
UapUsinpsi = (Ua + Usinpsi)
utpUcospsi = (Ut + Ucospsi)
utpUcospsi2 = utpUcospsi*utpUcospsi
UapUsinpsi2 = UapUsinpsi*UapUsinpsi
dR_dpsi = ((4.*U*r*arccos_piece*sin_psi*((16.*UapUsinpsi2)/(BB*pi2*f_wt_2) + 1.)**(0.5))/B -
(pi*U*(Ua*cos_psi - Ut*sin_psi)*(beta - np.arctan((Wa+Wa)/(Wt+Wt))))/(2.*(f_wt_2 + f_wa_2)**(0.5))
+ (pi*U*(f_wt_2 +f_wa_2)**(0.5)*(U + Utcospsi + Uasinpsi))/(2.*(f_wa_2/(f_wt_2) + 1.)*utpUcospsi2)
- (4.*U*piece*((16.*UapUsinpsi2)/(BB*pi2*f_wt_2) + 1.)**(0.5)*(R - r)*(Ut/2. -
(Ucospsi)/2.)*(U + Utcospsi + Uasinpsi ))/(f_wa_2*(1. - np.exp(-(B*(Wt+Wt)*(R -
r))/(r*(Wa+Wa))))**(0.5)) + (128.*U*r*arccos_piece*(Wa+Wa)*(Ut/2. - (Ucospsi)/2.)*(U +
Utcospsi + Uasinpsi ))/(BBB*pi2*utpUcospsi*utpUcospsi2*((16.*f_wa_2)/(BB*pi2*f_wt_2) + 1.)**(0.5)))
dR_dpsi[np.isnan(dR_dpsi)] = 0.1
dpsi = -Rsquiggly/dR_dpsi
psi = psi + dpsi
diff = np.max(abs(psiold-psi))
psiold = psi
# If its really not going to converge
if np.any(psi>(pi*85.0/180.)) and np.any(dpsi>0.0):
break
#This is an atrocious fit of DAE51 data at RE=50k for Cd
#There is also RE scaling
Re = (W*c)/nu
Cdval = (0.108*(Cl*Cl*Cl*Cl)-0.2612*(Cl*Cl*Cl)+0.181*(Cl*Cl)-0.0139*Cl+0.0278)*((50000./Re)**0.2)
Cdval[alpha>=pi/2] = 2.
#More Cd scaling from Mach from AA241ab notes for turbulent skin friction
Tw_Tinf = 1. + 1.78*(Ma*Ma)
Tp_Tinf = 1. + 0.035*(Ma*Ma) + 0.45*(Tw_Tinf-1.)
Tp = (Tp_Tinf)*T
Rp_Rinf = (Tp_Tinf**2.5)*(Tp+110.4)/(T+110.4)
Cd = ((1/Tp_Tinf)*(1/Rp_Rinf)**0.2)*Cdval
epsilon = Cd/Cl
epsilon[epsilon==np.inf] = 10.
deltar = (r[1]-r[0])
thrust = rho*B*(np.sum(Gamma*(Wt-epsilon*Wa)*deltar,axis=1)[:,None])
torque = rho*B*np.sum(Gamma*(Wa+epsilon*Wt)*r*deltar,axis=1)[:,None]
power = torque*omega
D = 2*R
Cp = power/(rho*(n*n*n)*(D*D*D*D*D))
thrust[conditions.propulsion.throttle[:,0] <=0.0] = 0.0
power[conditions.propulsion.throttle[:,0] <=0.0] = 0.0
thrust[omega1<0.0] = - thrust[omega1<0.0]
etap = V*thrust/power
conditions.propulsion.etap = etap
# store data
results_conditions = Data
conditions.propulsion.acoustic_outputs = results_conditions(
number_sections = N,
r0 = r,
airfoil_chord = c,
blades_number = B,
propeller_diameter = D,
drag_coefficient = Cd,
lift_coefficient = Cl,
omega = omega,
velocity = V,
thrust = thrust,
power = power,
mid_chord_aligment = self.prop_attributes.mid_chord_aligment
)
return thrust, torque, power, Cp
