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def get_centroid(aircraft):
"""Return the coordinates of the centroid."""
stringer_area = aircraft.stringer.area
cap_area = aircraft.spar.cap_area
caps_x = [value for spar in aircraft.spar.x for value in spar]
caps_z = [value for spar in aircraft.spar.z for value in spar]
stringers_x = aircraft.stringer.x
stringers_z = aircraft.stringer.z
denominator = float(
len(caps_x) * cap_area + len(stringers_x) * stringer_area)
centroid_x = float(
sum([x * cap_area
for x in caps_x]) + sum([x * stringer_area for x in stringers_x]))
centroid_x = centroid_x / denominator
centroid_z = float(
sum([z * cap_area
for z in caps_z]) + sum([z * stringer_area for z in stringers_z]))
centroid_z = centroid_z / denominator
return (centroid_x, centroid_z)
def get_inertia_terms(self):
"""Obtain all inertia terms."""
stringer_area = self.stringer.area
cap_area = self.spar.cap_area
# Adds upper and lower components' coordinates to list
x_stringers = self.stringer.x
z_stringers = self.stringer.z
x_spars = self.spar.x[:][0] + self.spar.x[:][1]
z_spars = self.spar.z[:][0] + self.spar.z[:][1]
stringer_count = range(len(x_stringers))
spar_count = range(len(self.spar.x))
# I_x is the sum of the contributions of the spar caps and stringers
# TODO: replace list indices with dictionary value
I_x = sum(
[cap_area * (z_spars[i] - self.centroid[1])**2 for i in spar_count])
I_x += sum([
stringer_area * (z_stringers[i] - self.centroid[1])**2
for i in stringer_count
])
I_z = sum(
[cap_area * (x_spars[i] - self.centroid[0])**2 for i in spar_count])
I_z += sum([
stringer_area * (x_stringers[i] - self.centroid[0])**2
for i in stringer_count
])
I_xz = sum([
cap_area * (x_spars[i] - self.centroid[0]) *
(z_spars[i] - self.centroid[1]) for i in spar_count
])
I_xz += sum([
stringer_area * (x_stringers[i] - self.centroid[0]) *
(z_stringers[i] - self.centroid[1]) for i in stringer_count
])
return (I_x, I_z, I_xz)
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