Source code for RCAIDE.Library.Methods.Geometry.Planform.convert_sweep
# ----------------------------------------------------------------------
# Imports
# ----------------------------------------------------------------------
import numpy as np
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# convert_sweep
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[docs]
def convert_sweep(wing,old_ref_chord_fraction = 0.0,new_ref_chord_fraction = 0.25):
""" This method converts the sweep of a wing planform to refer to a new
chord fraction. Defaults to converting from leading-edge sweep to
quarter-chord sweep.
Assumptions:
Assumes a simple trapezoidal wing shape. If the input wing object does
not have a simple trapezoidal shape, this function will convert sweeps
for an equivalent trapezoid having the same reference sweep, aspect
ratio, and taper ratio.
Source:
Unknown
Inputs:
wing - a data dictionary with the fields:
apsect_ratio - wing aspect ratio [dimensionless]
sweep - wing sweep [radians]
taper - wing taper ratio [dimensionless]
old_ref_chord_fraction - a float value between 0 and 1.0 that
tells what fraction of the local chord
the sweep line follows. (For example,
a value of 0.25 refers to quarter-chord
sweep
new_ref_chord_fraction - a float value between 0 and 1.0 that
tells what fraction of the local chord
is the new reference for sweep.
Outputs:
output - a single float value, new_sweep, which is the sweep
angle referenced to the new_ref_chord_fraction.
Defaults:
Defaults to converting from leading edge sweep to quater-chord sweep.
Properties Used:
N/A
"""
# Unpack inputs
sweep = wing.sweeps.quarter_chord
taper = wing.taper
if 'effective_aspect_ratio' in wing:
ar = wing.effective_aspect_ratio
elif 'extended' in wing:
if 'aspect_ratio' in wing.extended:
ar = wing.extended.aspect_ratio
else:
ar = wing.aspect_ratio
else:
ar = wing.aspect_ratio
#Convert sweep to leading edge sweep if it was not already so
if old_ref_chord_fraction == 0.0:
sweep_LE = wing.sweeps.leading_edge
else:
sweep_LE = np.arctan(np.tan(sweep)+4*old_ref_chord_fraction*
(1-taper)/(ar*(1+taper))) #Compute leading-edge sweep
#Convert from leading edge sweep to the desired sweep reference
new_sweep = np.arctan(np.tan(sweep_LE)-4*new_ref_chord_fraction*
(1-taper)/(ar*(1+taper))) #Compute sweep referenced
#to new chord-fraction
return new_sweep
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# Alternate Method
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[docs]
def convert_sweep_segments(old_sweep, seg_a, seg_b, wing, old_ref_chord_fraction=0.0, new_ref_chord_fraction=0.25):
""" This method converts the sweep of a section of a wing between two segments
to refer to a new chord fraction. More specifically, it converts the inboard
segment's (seg_a's) outboard sweep. Defaults to converting from leading-edge sweep to
quarter-chord sweep.
Assumptions:
Assumes a simple trapezoidal section shape. If the input section does
not have a simple trapezoidal shape, this function will convert sweeps
for an equivalent trapezoid having the same reference sweep, aspect
ratio, and taper ratio.
Source:
Unknown
Inputs:
old_sweep - sweep angle to convert
seg_a and seg_b - two Segment() objects with:
root_chord_percent - percent of the wing's root chord
wing - a data dictionary with the fields:
chords.root - root chord [m]
span - wingspan [m]
symmetric - symmetry [boolean]
old_ref_chord_fraction - a float value between 0 and 1.0 that
tells what fraction of the local chord
the sweep line follows. (For example,
a value of 0.25 refers to quarter-chord
sweep
new_ref_chord_fraction - a float value between 0 and 1.0 that
tells what fraction of the local chord
is the new reference for sweep.
Outputs:
output - a single float value, new_sweep, which is the sweep
angle referenced to the new_ref_chord_fraction.
Defaults:
Defaults to converting from leading edge sweep to quater-chord sweep.
Properties Used:
N/A
"""
if old_ref_chord_fraction==new_ref_chord_fraction:
return old_sweep
# Unpack inputs
sweep = old_sweep
root_chord = seg_a.root_chord_percent *wing.chords.root
tip_chord = seg_b.root_chord_percent *wing.chords.root
taper = tip_chord / root_chord
wingspan = wing.spans.projected if wing.symmetric else wing.spans.projected *2 #calculation is for full wingspan
section_span = wingspan *(seg_b.percent_span_location - seg_a.percent_span_location)
chord_mean_geo = 0.5 * (root_chord + tip_chord)
ar = section_span / chord_mean_geo
#Convert sweep to leading edge sweep if it was not already so
if old_ref_chord_fraction == 0.0:
sweep_LE = old_sweep
else:
sweep_LE = np.arctan(np.tan(sweep)+4*old_ref_chord_fraction*
(1-taper)/(ar*(1+taper))) #Compute leading-edge sweep
#Convert from leading edge sweep to the desired sweep reference
new_sweep = np.arctan(np.tan(sweep_LE)-4*new_ref_chord_fraction*
(1-taper)/(ar*(1+taper))) #Compute sweep referenced
#to new chord-fraction
return new_sweep
