Source code for RCAIDE.Library.Methods.Aerodynamics.Common.Drag.parasite_drag_nacelle
# RCAIDE/Library/Methods/Aerodynamics/Common/Drag/parasite_drag_nacelle.py
# (c) Copyright 2023 Aerospace Research Community LLC
#
# Created: Jun 2024, M. Clarke
# ----------------------------------------------------------------------------------------------------------------------
# IMPORT
# ----------------------------------------------------------------------------------------------------------------------
from RCAIDE.Framework.Core import Data
from RCAIDE.Library.Methods.Utilities import Cubic_Spline_Blender
from RCAIDE.Library.Methods.Aerodynamics.Common.Drag.compressible_turbulent_flat_plate import compressible_turbulent_flat_plate
# package imports
import numpy as np
# ----------------------------------------------------------------------------------------------------------------------
# Supersonic Parasite Drag Nacekke
# ----------------------------------------------------------------------------------------------------------------------
[docs]
def parasite_drag_nacelle(state,settings,geometry):
"""Computes the parasite drag due to the nacelle
Assumptions:
None
Source:
None
Args:
state.conditions.freestream.mach_number (numpy.ndarray): mach_number [Unitless]
state.conditions.freestream.temperature (numpy.ndarray): temperature [K]
state.conditions.freestream.reynolds_number (numpy.ndarray): Reynolds number [Unitless]
settings (dict): analyses settings [-]
geometry (dict): aircraft geometry [-]
Returns:
None
"""
# Estimating nacelle drag
for network in geometry.networks:
for propulsor in network.propulsors:
if 'nacelle' in propulsor:
nacelle_drag(state,settings,propulsor.nacelle)
return
# ----------------------------------------------------------------------------------------------------------------------
# Nacelle Drag
# ----------------------------------------------------------------------------------------------------------------------
[docs]
def nacelle_drag(state,settings, nacelle):
"""helperr fuction to computes the parasite drag due to the nacelle
Assumptions:
None
Source:
Stanford AA241 A/B Course Notes
Args:
state.conditions.freestream.mach_number (numpy.ndarray): mach_number [Unitless]
state.conditions.freestream.temperature (numpy.ndarray): temperature [K]
state.conditions.freestream.reynolds_number (numpy.ndarray): Reynolds number [Unitless]
settings (dict): analyses settings [-]
Returns:
None
"""
# unpack inputs
conditions = state.conditions
freestream = conditions.freestream
Mach = freestream.mach_number
T = freestream.temperature
Re = freestream.reynolds_number
low_mach_cutoff = settings.supersonic.begin_drag_rise_mach_number
high_mach_cutoff = settings.supersonic.end_drag_rise_mach_number
Sref = nacelle.diameter**2 / 4 * np.pi
Swet = nacelle.areas.wetted
# Reynolds number
Re_prop = Re*nacelle.length
# Skin friction coefficient
cf_prop, k_comp, k_reyn = compressible_turbulent_flat_plate(Re_prop,Mach,T)
# Form factor according to Raymer equation
form_factor = 1 + 0.35 / ( nacelle.length/nacelle.diameter)
if np.all((Mach<=1.0) == True):
# subsonic condition
parasite_drag = form_factor * cf_prop * Swet / Sref
else:
# supersonic condition
k_prop_sup = 1.
trans_spline = Cubic_Spline_Blender(low_mach_cutoff,high_mach_cutoff)
h00 = lambda M:trans_spline.compute(M)
form_factor = form_factor*(h00(Mach)) + k_prop_sup*(1-h00(Mach))
# find the final result
parasite_drag = form_factor * cf_prop * Swet / Sref
# store results
results = Data(
wetted_area = Swet ,
reference_area = Sref ,
total = parasite_drag ,
skin_friction = cf_prop ,
compressibility_factor = k_comp ,
reynolds_factor = k_reyn ,
form_factor = form_factor ,
)
state.conditions.aerodynamics.coefficients.drag.parasite[nacelle.tag] = results
return
