"""
FAST - Copyright (c) 2016 ONERA ISAE
"""
# This file is part of FAST-OAD : A framework for rapid Overall Aircraft Design
# Copyright (C) 2021 ONERA & ISAE-SUPAERO
# FAST is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <https://www.gnu.org/licenses/>.
import numpy as np
from openmdao.core.explicitcomponent import ExplicitComponent
[docs]class Cd0Wing(ExplicitComponent):
[docs] def initialize(self):
self.options.declare("low_speed_aero", default=False, types=bool)
[docs] def setup(self):
self.low_speed_aero = self.options["low_speed_aero"]
if self.low_speed_aero:
self.add_input("data:aerodynamics:wing:low_speed:reynolds", val=np.nan)
self.add_input(
"data:aerodynamics:aircraft:low_speed:CL", shape_by_conn=True, val=np.nan
)
self.add_input("data:aerodynamics:aircraft:takeoff:mach", val=np.nan)
self.add_output(
"data:aerodynamics:wing:low_speed:CD0",
copy_shape="data:aerodynamics:aircraft:low_speed:CL",
)
else:
self.add_input("data:aerodynamics:wing:cruise:reynolds", val=np.nan)
self.add_input("data:aerodynamics:aircraft:cruise:CL", shape_by_conn=True, val=np.nan)
self.add_input("data:TLAR:cruise_mach", val=np.nan)
self.add_output(
"data:aerodynamics:wing:cruise:CD0",
copy_shape="data:aerodynamics:aircraft:cruise:CL",
)
self.add_input("data:geometry:wing:area", val=np.nan, units="m**2")
self.add_input("data:geometry:wing:thickness_ratio", val=np.nan)
self.add_input("data:geometry:wing:wetted_area", val=np.nan, units="m**2")
self.add_input("data:geometry:wing:MAC:length", val=np.nan, units="m")
self.add_input("data:geometry:wing:sweep_25", val=np.nan, units="deg")
[docs] def setup_partials(self):
self.declare_partials("*", "*", method="fd")
[docs] def compute(self, inputs, outputs):
wing_area = inputs["data:geometry:wing:area"]
wet_area_wing = inputs["data:geometry:wing:wetted_area"]
el_aero = inputs["data:geometry:wing:thickness_ratio"]
sweep_25 = inputs["data:geometry:wing:sweep_25"]
l0_wing = inputs["data:geometry:wing:MAC:length"]
if self.low_speed_aero:
cl = inputs["data:aerodynamics:aircraft:low_speed:CL"]
mach = inputs["data:aerodynamics:aircraft:takeoff:mach"]
reynolds = inputs["data:aerodynamics:wing:low_speed:reynolds"]
else:
cl = inputs["data:aerodynamics:aircraft:cruise:CL"]
mach = inputs["data:TLAR:cruise_mach"]
reynolds = inputs["data:aerodynamics:wing:cruise:reynolds"]
ki_arrow_cd0 = 0.04
# Friction coefficients
cf_wing = 0.455 / ((1 + 0.144 * mach ** 2) ** 0.65 * (np.log10(reynolds * l0_wing)) ** 2.58)
# cd0 wing
# factor of relative thickness
ke_cd0_wing = 4.688 * el_aero ** 2 + 3.146 * el_aero
k_phi_cd0_wing = 1 - 0.000178 * sweep_25 ** 2 - 0.0065 * sweep_25
kc_cd0_wing = (
2.859 * (cl / np.cos(np.radians(sweep_25)) ** 2) ** 3
- 1.849 * (cl / np.cos(np.radians(sweep_25)) ** 2) ** 2
+ 0.382 * (cl / np.cos(np.radians(sweep_25)) ** 2)
+ 0.06
) # sweep factor
cd0_wing = (
((ke_cd0_wing + kc_cd0_wing) * k_phi_cd0_wing + ki_arrow_cd0 + 1)
* cf_wing
* wet_area_wing
/ wing_area
)
if self.low_speed_aero:
outputs["data:aerodynamics:wing:low_speed:CD0"] = cd0_wing
else:
outputs["data:aerodynamics:wing:cruise:CD0"] = cd0_wing