Source code for RCAIDE.Library.Methods.Aerodynamics.Common.Drag.estimate_2ndseg_lift_drag_ratio
# ----------------------------------------------------------------------
# Imports
# ----------------------------------------------------------------------
# RCAIDE Imports
from RCAIDE import *
from RCAIDE.Library.Components import Wings
from RCAIDE.Framework.Core import Units, Data
from RCAIDE.Library.Methods.Aerodynamics.Common.Lift import compute_max_lift_coeff
# ----------------------------------------------------------------------
# Compute 2nd segment lift to drag ratio
# ----------------------------------------------------------------------
[docs]
def estimate_2ndseg_lift_drag_ratio(state,settings,geometry):
"""Estimates the 2nd segment climb lift to drag ratio (all engine operating)
Assumptions:
All engines operating
Source:
Fig. 27.34 of "Aerodynamic Design of Transport Airplane" - Obert
Inputs:
config.
V2_VS_ratio [Unitless]
wings.
areas.reference [m^2]
spans.projected [m]
aspect_ratio [Unitless]
maximum_lift_coefficient [Unitless]
Outputs:
lift_drag_ratio [Unitless]
Properties Used:
N/A
"""
# ==============================================
# Unpack
# ==============================================
try:
V2_VS_ratio = geometry.V2_VS_ratio
except:
V2_VS_ratio = 1.20 # typical condition
# getting geometrical data (aspect ratio)
n_wing = 0
for wing in geometry.wings:
if not isinstance(wing,Wings.Main_Wing): continue
reference_area = wing.areas.reference
wing_span = wing.spans.projected
try:
aspect_ratio = wing.aspect_ratio
except:
aspect_ratio = wing_span ** 2 / reference_area
n_wing += 1
if n_wing > 1:
print(' More than one Main_Wing in the config. Last one will be considered.')
elif n_wing == 0:
print('No Main_Wing defined! Using the 1st wing found')
for wing in geometry.wings:
if not isinstance(wing,Wings.Wing): continue
reference_area = wing.areas.reference
wing_span = wing.spans.projected
try:
aspect_ratio = wing.aspect_ratio
except:
aspect_ratio = wing_span ** 2 / reference_area
break
# ==============================================
# Determining vehicle maximum lift coefficient
# ==============================================
maximum_lift_coefficient, induced_drag_high_lift = compute_max_lift_coeff(state,settings,geometry)
# Compute CL in V2
lift_coeff = maximum_lift_coefficient / (V2_VS_ratio ** 2)
# Estimate L/D in 2nd segment condition, ALL ENGINES OPERATIVE!
lift_drag_ratio = -6.464 * lift_coeff + 7.264 * aspect_ratio ** 0.5
return lift_drag_ratio
