"""Estimation of the landing gear profile drag."""
# This file is part of FAST-OAD_CS23 : A framework for rapid Overall Aircraft Design
# Copyright (C) 2022 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
import fastoad.api as oad
from openmdao.core.explicitcomponent import ExplicitComponent
from ..constants import SUBMODEL_CD0_LANDING_GEAR
[docs]@oad.RegisterSubmodel(
SUBMODEL_CD0_LANDING_GEAR, "fastga.submodel.aerodynamics.landing_gear.cd0.legacy"
)
class Cd0LandingGear(ExplicitComponent):
"""
Profile drag estimation for the landing gear
Based on : Gudmundsson, Snorri. General aviation aircraft design: Applied Methods and
Procedures. Butterworth-Heinemann, 2013.
"""
[docs] def initialize(self):
self.options.declare("low_speed_aero", default=False, types=bool)
[docs] def setup(self):
self.add_input("data:geometry:landing_gear:type", val=np.nan)
self.add_input("data:geometry:landing_gear:height", val=np.nan, units="m")
self.add_input("data:geometry:wing:area", val=np.nan, units="m**2")
if self.options["low_speed_aero"]:
self.add_output("data:aerodynamics:landing_gear:low_speed:CD0")
self.declare_partials(
"data:aerodynamics:landing_gear:low_speed:CD0",
["data:geometry:landing_gear:height", "data:geometry:wing:area"],
method="exact",
)
else:
self.add_output("data:aerodynamics:landing_gear:cruise:CD0")
self.declare_partials(
"data:aerodynamics:landing_gear:cruise:CD0",
["data:geometry:landing_gear:height", "data:geometry:wing:area"],
method="exact",
)
[docs] def compute(self, inputs, outputs, discrete_inputs=None, discrete_outputs=None):
lg_type = inputs["data:geometry:landing_gear:type"]
lg_height = inputs["data:geometry:landing_gear:height"]
wing_area = inputs["data:geometry:wing:area"]
if lg_type == 0.0: # non-retractable LG AC (ref: Cirrus SR22)
# Gudmundsson example 15.12 (page 721)
area_mlg = 15 * 6 * 0.0254**2 # Frontal area of wheel (data in inches)
area_nlg = 14 * 5 * 0.0254**2
# MLG
cd_wheel = 0.484
cd0_mlg = cd_wheel * area_mlg / wing_area
# NLG
cd_wheel = 0.484 / 2
cd0_nlg = cd_wheel * area_nlg / wing_area
cd0 = cd0_mlg + cd0_nlg
if self.options["low_speed_aero"]:
outputs["data:aerodynamics:landing_gear:low_speed:CD0"] = cd0
else:
outputs["data:aerodynamics:landing_gear:cruise:CD0"] = cd0
else: # retractable LG AC
tyre_width = 5 * 0.0254
# MLG
cd_mlg = 1.2
area_mlg = tyre_width * 1.8 * lg_height
# NLG
cd_nlg = 0.65
area_nlg = 14 * 5 * 0.0254**2
cd0 = (cd_mlg * area_mlg + cd_nlg * area_nlg) / wing_area
if self.options["low_speed_aero"]:
outputs["data:aerodynamics:landing_gear:low_speed:CD0"] = cd0
else:
outputs["data:aerodynamics:landing_gear:cruise:CD0"] = 0.0
[docs] def compute_partials(self, inputs, partials, discrete_inputs=None):
lg_type = inputs["data:geometry:landing_gear:type"]
lg_height = inputs["data:geometry:landing_gear:height"]
wing_area = inputs["data:geometry:wing:area"]
if lg_type == 0.0:
area_mlg = 15 * 6 * 0.0254**2 # Frontal area of wheel (data in inches)
area_nlg = 14 * 5 * 0.0254**2
# MLG
cd_wheel = 0.484
cd0_mlg = cd_wheel * area_mlg / wing_area
# NLG
cd_wheel = 0.484 / 2
cd0_nlg = cd_wheel * area_nlg / wing_area
cd0 = cd0_mlg + cd0_nlg
if self.options["low_speed_aero"]:
partials[
"data:aerodynamics:landing_gear:low_speed:CD0",
"data:geometry:landing_gear:height",
] = 0
partials[
"data:aerodynamics:landing_gear:low_speed:CD0",
"data:geometry:wing:area",
] = -cd0 / wing_area
else:
partials[
"data:aerodynamics:landing_gear:cruise:CD0", "data:geometry:landing_gear:height"
] = 0
partials[
"data:aerodynamics:landing_gear:cruise:CD0",
"data:geometry:wing:area",
] = -cd0 / wing_area
else:
tyre_width = 5 * 0.0254
# MLG
cd_mlg = 1.2
area_mlg = tyre_width * 1.8 * lg_height
# NLG
cd_nlg = 0.65
area_nlg = 14 * 5 * 0.0254**2
cd0 = (cd_mlg * area_mlg + cd_nlg * area_nlg) / wing_area
if self.options["low_speed_aero"]:
partials[
"data:aerodynamics:landing_gear:low_speed:CD0",
"data:geometry:landing_gear:height",
] = cd_mlg * tyre_width * 1.8 / wing_area
partials[
"data:aerodynamics:landing_gear:low_speed:CD0",
"data:geometry:wing:area",
] = -cd0 / wing_area
else:
partials[
"data:aerodynamics:landing_gear:cruise:CD0", "data:geometry:landing_gear:height"
] = 0.0
partials[
"data:aerodynamics:landing_gear:cruise:CD0",
"data:geometry:wing:area",
] = 0.0