From 8b6f11119790c8c930734894a37d2a4aaa42462d Mon Sep 17 00:00:00 2001
From: blendoit <blendoit@gmail.com>
Date: Fri, 1 Nov 2019 18:12:34 -0700
Subject: Start work on optimized multiprocessing random a/c gen. & eval.

---
 aircraftstudio/__init__.py            |   1 +
 aircraftstudio/creator/__init__.py    |   4 +
 aircraftstudio/creator/base.py        | 112 ++++++++++++
 aircraftstudio/creator/fuselage.py    |   0
 aircraftstudio/creator/propulsion.py  |   0
 aircraftstudio/creator/wing.py        | 312 ++++++++++++++++++++++++++++++++++
 aircraftstudio/evaluator/__init__.py  |   1 +
 aircraftstudio/evaluator/dP.py        |  18 ++
 aircraftstudio/evaluator/drag.py      |  18 ++
 aircraftstudio/evaluator/evaluator.py | 195 +++++++++++++++++++++
 aircraftstudio/evaluator/inertia.py   |  66 +++++++
 aircraftstudio/evaluator/lift.py      |  30 ++++
 aircraftstudio/evaluator/mass.py      |   8 +
 aircraftstudio/generator/__init__.py  |   1 +
 aircraftstudio/generator/generator.py |  43 +++++
 15 files changed, 809 insertions(+)
 create mode 100644 aircraftstudio/__init__.py
 create mode 100644 aircraftstudio/creator/__init__.py
 create mode 100644 aircraftstudio/creator/base.py
 create mode 100644 aircraftstudio/creator/fuselage.py
 create mode 100644 aircraftstudio/creator/propulsion.py
 create mode 100644 aircraftstudio/creator/wing.py
 create mode 100644 aircraftstudio/evaluator/__init__.py
 create mode 100644 aircraftstudio/evaluator/dP.py
 create mode 100644 aircraftstudio/evaluator/drag.py
 create mode 100644 aircraftstudio/evaluator/evaluator.py
 create mode 100644 aircraftstudio/evaluator/inertia.py
 create mode 100644 aircraftstudio/evaluator/lift.py
 create mode 100644 aircraftstudio/evaluator/mass.py
 create mode 100644 aircraftstudio/generator/__init__.py
 create mode 100644 aircraftstudio/generator/generator.py

(limited to 'aircraftstudio')

diff --git a/aircraftstudio/__init__.py b/aircraftstudio/__init__.py
new file mode 100644
index 0000000..dda0cea
--- /dev/null
+++ b/aircraftstudio/__init__.py
@@ -0,0 +1 @@
+from . import creator, evaluator, generator
diff --git a/aircraftstudio/creator/__init__.py b/aircraftstudio/creator/__init__.py
new file mode 100644
index 0000000..818c7b2
--- /dev/null
+++ b/aircraftstudio/creator/__init__.py
@@ -0,0 +1,4 @@
+from . import base
+from . import fuselage
+from . import propulsion
+from . import wing
diff --git a/aircraftstudio/creator/base.py b/aircraftstudio/creator/base.py
new file mode 100644
index 0000000..92fe421
--- /dev/null
+++ b/aircraftstudio/creator/base.py
@@ -0,0 +1,112 @@
+"""The base.py module contains parent classes for components."""
+
+import numpy as np
+import os.path
+import random
+import logging
+
+from aircraftstudio import creator
+
+logging.basicConfig(filename='log_base.txt',
+                    level=logging.DEBUG,
+                    format='%(asctime)s - %(levelname)s - %(message)s')
+
+
+class Aircraft:
+    """This class tracks all sub-components and is fed to the evaluator."""
+    name = None
+    fuselage = None
+    propulsion = None
+    wing = None
+    properties = {}
+
+    naca = [2412, 3412, 2420]
+
+    def __init__(self):
+        self.results = {}
+
+    def __str__(self):
+        return self.name
+
+    @classmethod
+    def from_default(cls):
+        aircraft = Aircraft()
+        aircraft.name = 'default_aircraft_' + str(random.randrange(1000, 9999))
+        airfoil = creator.wing.Airfoil(aircraft, 'default_airfoil')
+        airfoil.add_naca(2412)
+        soar1 = creator.wing.Spar(airfoil, 'default_spar_1', 0.30)
+        soar2 = creator.wing.Spar(airfoil, 'default_spar_2', 0.60)
+        stringer = creator.wing.Stringer(airfoil, 'default_stringer')
+        return aircraft
+
+    @classmethod
+    def from_random(cls):
+        aircraft = Aircraft()
+        aircraft.name = 'random_aircraft_' + str(random.randrange(1000, 9999))
+        airfoil = creator.wing.Airfoil(aircraft, 'random_airfoil')
+        airfoil.add_naca(random.choice(cls.naca))
+        soar1 = creator.wing.Spar(airfoil, 'random_spar_1',
+                                  random.randrange(20, 80) / 100)
+        soar2 = creator.wing.Spar(airfoil, 'random_spar_2',
+                                  random.randrange(20, 80) / 100)
+        stringer = creator.wing.Stringer(airfoil, 'random_stringer',
+                                         random.randint(1, 10),
+                                         random.randint(1, 10),
+                                         random.randint(1, 10),
+                                         random.randint(1, 10))
+        return aircraft
+
+
+class Component:
+    """Basic component providing coordinates, tools and a component tree."""
+    def __init__(self, parent, name):
+        self.parent = parent
+        self.name = name
+        self.x = np.array([])
+        self.z = np.array([])
+        self.y = np.array([])
+        self.material = None
+        self.mass = float()
+        self.properties = {}
+
+    def __str__(self):
+        return self.name
+
+    def info_print(self, round):
+        """Print all the component's coordinates to the terminal."""
+        name = f'    CREATOR DATA FOR {str(self).upper()}    '
+        num_of_dashes = len(name)
+        print(num_of_dashes * '-')
+        print(name)
+        for k, v in self.__dict__.items():
+            if type(v) is not np.ndarray:
+                print(f'{k}:\n', v)
+                print(num_of_dashes * '-')
+        for k, v in self.__dict__.items():
+            if type(v) is np.ndarray:
+                print(f'{k}:\n', np.around(v, round))
+        return None
+
+    def info_save(self,
+                  save_path='/home/blendux/Projects/Aircraft_Studio/save'):
+        """Save all the object's coordinates (must be full path)."""
+        file_name = f'{self.name}_info.txt'
+        full_path = os.path.join(save_path, file_name)
+        try:
+            with open(full_path, 'w') as f:
+                for k, v in self.__dict__.items():
+                    if type(v) is not np.ndarray:
+                        f.write(f'{k}=\n')
+                        f.write(str(v))
+                        f.write("\n")
+                        # print(num_of_dashes * '-')
+                for k, v in self.__dict__.items():
+                    if type(v) is np.ndarray:
+                        f.write(f'{k}=\n')
+                        f.write(str(v))
+                        f.write("\n")
+            logging.debug(f'Successfully wrote to file {full_path}')
+        except IOError:
+            print(f'Unable to write {file_name} to specified directory.\n',
+                  'Was the full path passed to the function?')
+        return None
diff --git a/aircraftstudio/creator/fuselage.py b/aircraftstudio/creator/fuselage.py
new file mode 100644
index 0000000..e69de29
diff --git a/aircraftstudio/creator/propulsion.py b/aircraftstudio/creator/propulsion.py
new file mode 100644
index 0000000..e69de29
diff --git a/aircraftstudio/creator/wing.py b/aircraftstudio/creator/wing.py
new file mode 100644
index 0000000..afe52fe
--- /dev/null
+++ b/aircraftstudio/creator/wing.py
@@ -0,0 +1,312 @@
+"""
+The wing.py module contains class definitions for and various components
+we add to an airfoil (spars, stringers, and ribs).
+
+Classes:
+    Airfoil: instantiated with class method to provide coordinates to heirs.
+    Spar: inherits from Airfoil.
+    Stringer: also inherits from Airfoil.
+
+Functions:
+    plot_geom(airfoil): generates a 2D plot of the airfoil & any components.
+"""
+
+import logging
+import numpy as np
+from math import sin, cos, atan
+import bisect as bi
+import matplotlib.pyplot as plt
+
+from aircraftstudio.creator import base
+import resources.materials as mt
+
+
+class Airfoil(base.Component):
+    """This class represents a single NACA airfoil.
+
+    The coordinates are saved as two np.arrays
+    for the x- and z-coordinates. The coordinates start at
+    the leading edge, travel over the airfoil's upper edge,
+    then loop back to the leading edge via the lower edge.
+
+    This method was chosen for easier future exports
+    to 3D CAD packages like SolidWorks, which can import such
+    geometry as coordinates written in a CSV file.
+    """
+    def __init__(self,
+                 parent,
+                 name,
+                 chord=68,
+                 semi_span=150,
+                 material=mt.aluminium):
+        super().__init__(parent, name)
+        parent.wing = self
+        if chord > 20:
+            self.chord = chord
+        else:
+            self.chord = 20
+            logging.debug('Chord too small, using minimum value of 20.')
+        parent
+        self.semi_span = semi_span
+        self.material = material
+        self.spars = []
+        self.stringers = []
+
+    def add_naca(self, naca_num=2412):
+        """Generate surface geometry for a NACA airfoil.
+
+        The nested functions perform the required steps to generate geometry,
+        and can be called to solve the geometry y-coordinate for any 'x' input.
+        Equation coefficients were retrieved from Wikipedia.org.
+
+        Parameters:
+        naca_num: 4-digit NACA wing
+
+        Return:
+        None
+        """
+        self.naca_num = naca_num
+        # Variables extracted from naca_num argument passed to the function
+        m = int(str(naca_num)[0]) / 100
+        p = int(str(naca_num)[1]) / 10
+        t = int(str(naca_num)[2:]) / 100
+        # x-coordinate of maximum camber
+        p_c = p * self.chord
+
+        def get_camber(x):
+            """
+            Returns camber z-coordinate from 1 'x' along the airfoil chord.
+            """
+            z_c = float()
+            if 0 <= x < p_c:
+                z_c = (m / (p**2)) * (2 * p * (x / self.chord) -
+                                      (x / self.chord)**2)
+            elif p_c <= x <= self.chord:
+                z_c = (m /
+                       ((1 - p)**2)) * ((1 - 2 * p) + 2 * p *
+                                        (x / self.chord) - (x / self.chord)**2)
+            return (z_c * self.chord)
+
+        def get_thickness(x):
+            """Return thickness from 1 'x' along the airfoil chord."""
+            x = 0 if x < 0 else x
+            z_t = 5 * t * self.chord * (+0.2969 *
+                                        (x / self.chord)**0.5 - 0.1260 *
+                                        (x / self.chord)**1 - 0.3516 *
+                                        (x / self.chord)**2 + 0.2843 *
+                                        (x / self.chord)**3 - 0.1015 *
+                                        (x / self.chord)**4)
+            return z_t
+
+        def get_theta(x):
+            dz_c = float()
+            if 0 <= x < p_c:
+                dz_c = ((2 * m) / p**2) * (p - x / self.chord)
+            elif p_c <= x <= self.chord:
+                dz_c = (2 * m) / ((1 - p)**2) * (p - x / self.chord)
+
+            theta = atan(dz_c)
+            return theta
+
+        def get_coord_u(x):
+            x = x - get_thickness(x) * sin(get_theta(x))
+            z = get_camber(x) + get_thickness(x) * cos(get_theta(x))
+            return (x, z)
+
+        def get_coord_l(x):
+            x = x + get_thickness(x) * sin(get_theta(x))
+            z = get_camber(x) - get_thickness(x) * cos(get_theta(x))
+            return (x, z)
+
+        # Densify x-coordinates 10 times for first 1/4 chord length
+        x_chord_25_percent = round(self.chord / 4)
+        x_chord = [i / 10 for i in range(x_chord_25_percent * 10)]
+        x_chord.extend(i for i in range(x_chord_25_percent, self.chord + 1))
+        # Generate our airfoil skin geometry from previous sub-functions
+        self.x_c = np.array([])
+        self.z_c = np.array([])
+        # Upper surface and camber line
+        for x in x_chord:
+            self.x_c = np.append(self.x_c, x)
+            self.z_c = np.append(self.z_c, get_camber(x))
+            self.x = np.append(self.x, get_coord_u(x)[0])
+            self.z = np.append(self.z, get_coord_u(x)[1])
+        # Lower surface
+        for x in x_chord[::-1]:
+            self.x = np.append(self.x, get_coord_l(x)[0])
+            self.z = np.append(self.z, get_coord_l(x)[1])
+        return None
+
+
+class Spar(base.Component):
+    """Contains a single spar's data."""
+    def __init__(self, parent, name, loc_percent=0.30, material=mt.aluminium):
+        """Set spar location as percent of chord length."""
+        super().__init__(parent, name)
+        parent.spars.append(self)
+        self.material = material
+        self.cap_area = float()
+        # bi.bisect_left: returns index of first value in parent.x > loc
+        # This ensures that spar geom intersects with airfoil geom.
+        loc = loc_percent * parent.chord
+        # Spar upper coordinates
+        spar_u = bi.bisect_left(parent.x, loc) - 1
+        self.x = np.append(self.x, parent.x[spar_u])
+        self.z = np.append(self.z, parent.z[spar_u])
+        # Spar lower coordinates
+        spar_l = bi.bisect_left(parent.x[::-1], loc)
+        self.x = np.append(self.x, parent.x[-spar_l])
+        self.z = np.append(self.z, parent.z[-spar_l])
+        return None
+
+    def set_cap_area(self, cap_area):
+        self.cap_area = cap_area
+        return None
+
+    def set_mass(self, mass):
+        self.mass = mass
+        return None
+
+
+class Stringer(base.Component):
+    """Contains the coordinates of all stringers."""
+    def __init__(self,
+                 parent,
+                 name,
+                 den_u_1=4,
+                 den_u_2=4,
+                 den_l_1=4,
+                 den_l_2=4):
+        """Add equally distributed stringers to four airfoil locations
+        (upper nose, lower nose, upper surface, lower surface).
+
+        den_u_1: upper nose number of stringers
+        den_u_2: upper surface number of stringers
+        den_l_1: lower nose number of stringers
+        den_l_2: lower surface number of stringers
+        """
+        super().__init__(parent, name)
+        parent.stringers = self
+        self.x_start = []
+        self.x_end = []
+        self.z_start = []
+        self.z_end = []
+        self.diameter = float()
+        self.area = float()
+
+        # Find distance between leading edge and first upper stringer
+        # interval = self.parent.spars[0].x[0] / (den_u_1 + 1)
+        interval = 2
+        # initialise first self.stringer_x at first interval
+        x = interval
+        # Add upper stringers from leading edge until first spar.
+        for _ in range(0, den_u_1):
+            # Index of the first value of airfoil.x > x
+            i = bi.bisect_left(self.parent.x, x)
+            self.x = np.append(self.x, self.parent.x[i])
+            self.z = np.append(self.z, self.parent.z[i])
+            x += interval
+            # Add upper stringers from first spar until last spar
+        interval = (self.parent.spars[-1].x[0] -
+                    self.parent.spars[0].x[0]) / (den_u_2 + 1)
+        x = interval + self.parent.spars[0].x[0]
+        for _ in range(0, den_u_2):
+            i = bi.bisect_left(self.parent.x, x)
+            self.x = np.append(self.x, self.parent.x[i])
+            self.z = np.append(self.z, self.parent.z[i])
+            x += interval
+
+        # Find distance between leading edge and first lower stringer
+        interval = self.parent.spars[0].x[1] / (den_l_1 + 1)
+        x = interval
+        # Add lower stringers from leading edge until first spar.
+        for _ in range(0, den_l_1):
+            i = bi.bisect_left(self.parent.x[::-1], x)
+            self.x = np.append(self.x, self.parent.x[-i])
+            self.z = np.append(self.z, self.parent.z[-i])
+            x += interval
+            # Add lower stringers from first spar until last spar
+        interval = (self.parent.spars[-1].x[1] -
+                    self.parent.spars[0].x[1]) / (den_l_2 + 1)
+        x = interval + self.parent.spars[0].x[1]
+        for _ in range(0, den_l_2):
+            i = bi.bisect_left(self.parent.x[::-1], x)
+            self.x = np.append(self.x, self.parent.x[-i])
+            self.z = np.append(self.z, self.parent.z[-i])
+            x += interval
+        return None
+
+    def add_area(self, area):
+        self.area = area
+        return None
+
+    def add_mass(self, mass):
+        self.mass = len(self.x) * mass + len(self.x) * mass
+        return None
+
+    def add_webs(self, thickness):
+        """Add webs to stringers."""
+        for _ in range(len(self.x) // 2):
+            self.x_start.append(self.x[_])
+            self.x_end.append(self.x[_ + 1])
+            self.z_start.append(self.z[_])
+            self.z_end.append(self.z[_ + 1])
+            self.thickness = thickness
+        return None
+
+    def info_print(self, round=2):
+        super().info_print(round)
+        print('Stringer Area:\n', np.around(self.area, round))
+        return None
+
+
+def plot_geom(airfoil):
+    """This function plots the airfoil's + sub-components' geometry."""
+    fig, ax = plt.subplots()
+
+    # Plot chord
+    x = [0, airfoil.chord]
+    y = [0, 0]
+    ax.plot(x, y, linewidth='1')
+    # Plot quarter chord
+    ax.plot(airfoil.chord / 4,
+            0,
+            '.',
+            color='g',
+            markersize=24,
+            label='Quarter-chord')
+    # Plot mean camber line
+    ax.plot(airfoil.x_c,
+            airfoil.z_c,
+            '-.',
+            color='r',
+            linewidth='2',
+            label='Mean camber line')
+    # Plot airfoil surfaces
+    ax.plot(airfoil.x, airfoil.z, color='b', linewidth='1')
+
+    try:  # Plot spars
+        for spar in airfoil.spars:
+            x = (spar.x)
+            y = (spar.z)
+            ax.plot(x, y, '-', color='y', linewidth='4')
+    except AttributeError:
+        print('No spars to plot.')
+    try:  # Plot stringers
+        for i in range(len(airfoil.stringers.x)):
+            x = airfoil.stringers.x[i]
+            y = airfoil.stringers.z[i]
+            ax.plot(x, y, '.', color='y', markersize=12)
+    except AttributeError:
+        print('No stringers to plot.')
+
+    ax.set(title='NACA ' + str(airfoil.naca_num) + ' airfoil',
+           xlabel='X axis',
+           ylabel='Z axis')
+
+    plt.grid(axis='both', linestyle=':', linewidth=1)
+    plt.gca().set_aspect('equal', adjustable='box')
+    plt.gca().legend(bbox_to_anchor=(1, 1),
+                     bbox_transform=plt.gcf().transFigure)
+    plt.show()
+    return fig, ax
diff --git a/aircraftstudio/evaluator/__init__.py b/aircraftstudio/evaluator/__init__.py
new file mode 100644
index 0000000..a58168b
--- /dev/null
+++ b/aircraftstudio/evaluator/__init__.py
@@ -0,0 +1 @@
+from .evaluator import *
diff --git a/aircraftstudio/evaluator/dP.py b/aircraftstudio/evaluator/dP.py
new file mode 100644
index 0000000..b6aaa3b
--- /dev/null
+++ b/aircraftstudio/evaluator/dP.py
@@ -0,0 +1,18 @@
+def get_dx(self, component):
+    return [x - self.centroid[0] for x in component.x_start]
+
+
+def get_dz(self, component):
+    return [x - self.centroid[1] for x in component.x_start]
+
+
+def get_dP(self, xDist, zDist, V_x, V_z, area):
+    I_x = self.I_['x']
+    I_z = self.I_['z']
+    I_xz = self.I_['xz']
+    denom = float(I_x * I_z - I_xz**2)
+    z = float()
+    for _ in range(len(xDist)):
+        z += float(-area * xDist[_] * (I_x * V_x - I_xz * V_z) / denom -
+                   area * zDist[_] * (I_z * V_z - I_xz * V_x) / denom)
+    return z
diff --git a/aircraftstudio/evaluator/drag.py b/aircraftstudio/evaluator/drag.py
new file mode 100644
index 0000000..73a26fc
--- /dev/null
+++ b/aircraftstudio/evaluator/drag.py
@@ -0,0 +1,18 @@
+import random
+
+def get_drag(aircraft, drag):
+    # Transform semi-span integer into list
+    semi_span = [x for x in range(0, aircraft.wing.semi_span)]
+
+    # Drag increases after 80% of the semi_span
+    cutoff = round(0.8 * aircraft.wing.span)
+
+    # Drag increases by 25% after 80% of the semi_span
+    F_x = [drag for x in semi_span[0:cutoff]]
+    F_x.extend([1.25 * drag for x in semi_span[cutoff:]])
+    return F_x
+
+
+def get_drag_total(aircraft):
+    """Get total drag force acting on the aircraft."""
+    return random.random() * 100
diff --git a/aircraftstudio/evaluator/evaluator.py b/aircraftstudio/evaluator/evaluator.py
new file mode 100644
index 0000000..18bb692
--- /dev/null
+++ b/aircraftstudio/evaluator/evaluator.py
@@ -0,0 +1,195 @@
+"""
+The evaluator.py module contains functions
+that return calculated data for an aircraft.
+Plotting aircraft components is also possible.
+"""
+
+import os.path
+import concurrent.futures
+import matplotlib.pyplot as plt
+
+from . import drag, inertia, lift, mass
+
+
+def analyze(aircraft):
+    """Analyze a single aircraft."""
+    results = {
+        'Lift': lift.get_lift_total(aircraft),
+        'Drag': drag.get_drag_total(aircraft),
+        'Mass': mass.get_mass_total(aircraft),
+        'Centroid': inertia.get_centroid(aircraft)
+    }
+    aircraft.results = results
+    return aircraft.name, results
+
+
+def analyze_all(population):
+    """Analyze all aircraft in a given population."""
+    # for aircraft in population.aircrafts:
+    #     print(analyze(aircraft))
+    with concurrent.futures.ProcessPoolExecutor() as executor:
+        results = executor.map(analyze, population.aircrafts)
+        for result in results:
+            print(result)
+    return None
+
+    # def analysis(self, V_x, V_z):
+    #     """Perform all analysis calculations and store in class instance."""
+
+    #     self.drag = self.get_drag(10)
+    #     self.lift_rectangular = self.get_lift_rectangular(13.7)
+    #     self.lift_elliptical = self.get_lift_elliptical(15)
+    #     self.lift_total = self.get_lift_total()
+    #     self.mass_dist = self.get_mass_distribution(self.mass_total)
+    #     self.centroid = self.get_centroid()
+    #     self.I_['x'] = self.get_inertia_terms()[0]
+    #     self.I_['z'] = self.get_inertia_terms()[1]
+    #     self.I_['xz'] = self.get_inertia_terms()[2]
+    #     spar_dx = self.get_dx(self.spar)
+    #     spar_dz = self.get_dz(self.spar)
+    #     self.spar.dP_x = self.get_dP(spar_dx, spar_dz, V_x, 0,
+    #                                  self.spar.cap_area)
+    #     self.spar.dP_z = self.get_dP(spar_dx, spar_dz, 0, V_z,
+    #                                  self.spar.cap_area)
+    #     print("yayyyyy")
+    #     return None
+
+    # print(f"Analysis results for {aircraft.name}:\n", results)
+    # self.results = self.get_lift_total(aircraft)
+
+    # self.drag = self.get_drag(10)
+    # self.lift_rectangular = self.get_lift_rectangular(13.7)
+    # self.lift_elliptical = self.get_lift_elliptical(15)
+    # self.lift_total = self.get_lift_total()
+    # self.mass_dist = self.get_mass_distribution(self.mass_total)
+    # self.centroid = self.get_centroid()
+    # self.I_['x'] = self.get_inertia_terms()[0]
+    # self.I_['z'] = self.get_inertia_terms()[1]
+    # self.I_['xz'] = self.get_inertia_terms()[2]
+    # spar_dx = self.get_dx(self.spar)
+    # spar_dz = self.get_dz(self.spar)
+    # self.spar.dP_x = self.get_dP(spar_dx, spar_dz, V_x, 0,
+    #                              self.spar.cap_area)
+    # self.spar.dP_z = self.get_dP(spar_dx, spar_dz, 0, V_z,
+    #                              self.spar.cap_area)
+    # return None
+
+    def tree_print(self, population):
+        """Print the list of subcomponents."""
+        name = f"    TREE FOR {[i.name for i in population.aircraft]} IN {self.name}    "
+        num_of_dashes = len(name)
+        print(num_of_dashes * '-')
+        print(name)
+        for aircraft in population:
+            print(".")
+            print(f"`-- {aircraft}")
+            print(f"    |--{aircraft.wing}")
+            print(f"    |   |-- {aircraft.wing.stringers}")
+            for spar in aircraft.wing.spars[:-1]:
+                print(f"    |   |-- {spar}")
+            print(f"    |   `-- {aircraft.wing.spars[-1]}")
+            print(f"    |-- {aircraft.fuselage}")
+            print(f"    `-- {aircraft.propulsion}")
+        print(num_of_dashes * '-')
+        return None
+
+    def tree_save(self,
+                  population,
+                  save_path='/home/blendux/Projects/Aircraft_Studio/save'):
+        """Save the evaluator's tree to a file."""
+        for aircraft in population.aircraft:
+            file_name = f"{aircraft.name}_tree.txt"
+            full_path = os.path.join(save_path, file_name)
+            with open(full_path, 'w') as f:
+                try:
+                    f.write(".\n")
+                    f.write(f"`-- {aircraft}\n")
+                    f.write(f"    |--{aircraft.wing}\n")
+                    for spar in aircraft.wing.spars[:-1]:
+                        f.write(f"    |   |-- {spar}\n")
+                    f.write(f"    |   `-- {aircraft.wing.spars[-1]}\n")
+                    f.write(f"    |-- {aircraft.fuselage}\n")
+                    f.write(f"    `-- {aircraft.propulsion}\n")
+                    logging.debug(f'Successfully wrote to file {full_path}')
+
+                except IOError:
+                    print(
+                        f'Unable to write {file_name} to specified directory.',
+                        'Was the full path passed to the function?')
+        return None
+
+
+def plot_geom(evaluator):
+    """This function plots analysis results over the airfoil's geometry."""
+    # Plot chord
+    x_chord = [0, evaluator.chord]
+    y_chord = [0, 0]
+    plt.plot(x_chord, y_chord, linewidth='1')
+    # Plot quarter chord
+    plt.plot(evaluator.chord / 4,
+             0,
+             '.',
+             color='g',
+             markersize=24,
+             label='Quarter-chord')
+    # Plot airfoil surfaces
+    x = [0.98 * x for x in evaluator.airfoil.x]
+    y = [0.98 * z for z in evaluator.airfoil.z]
+    plt.fill(x, y, color='w', linewidth='1', fill=False)
+    x = [1.02 * x for x in evaluator.airfoil.x]
+    y = [1.02 * z for z in evaluator.airfoil.z]
+    plt.fill(x, y, color='b', linewidth='1', fill=False)
+
+    # Plot spars
+    try:
+        for _ in range(len(evaluator.spar.x)):
+            x = (evaluator.spar.x[_])
+            y = (evaluator.spar.z[_])
+            plt.plot(x, y, '-', color='b')
+    except AttributeError:
+        print('No spars to plot.')
+    # Plot stringers
+    try:
+        for _ in range(0, len(evaluator.stringer.x)):
+            x = evaluator.stringer.x[_]
+            y = evaluator.stringer.z[_]
+            plt.plot(x, y, '.', color='y', markersize=12)
+    except AttributeError:
+        print('No stringers to plot.')
+
+    # Plot centroid
+    x = evaluator.centroid[0]
+    y = evaluator.centroid[1]
+    plt.plot(x, y, '.', color='r', markersize=24, label='centroid')
+
+    # Graph formatting
+    plt.xlabel('X axis')
+    plt.ylabel('Z axis')
+
+    plot_bound = max(evaluator.airfoil.x)
+    plt.xlim(-0.10 * plot_bound, 1.10 * plot_bound)
+    plt.ylim(-(1.10 * plot_bound / 2), (1.10 * plot_bound / 2))
+    plt.gca().set_aspect('equal', adjustable='box')
+    plt.gca().legend()
+    plt.grid(axis='both', linestyle=':', linewidth=1)
+    plt.show()
+    return None
+
+
+def plot_lift(evaluator):
+    x = range(evaluator.semi_span)
+    y_1 = evaluator.lift_rectangular
+    y_2 = evaluator.lift_elliptical
+    y_3 = evaluator.lift_total
+    plt.plot(x, y_1, '.', color='b', markersize=4, label='Rectangular lift')
+    plt.plot(x, y_2, '.', color='g', markersize=4, label='Elliptical lift')
+    plt.plot(x, y_3, '.', color='r', markersize=4, label='Total lift')
+
+    # Graph formatting
+    plt.xlabel('Semi-span location')
+    plt.ylabel('Lift')
+
+    plt.gca().legend()
+    plt.grid(axis='both', linestyle=':', linewidth=1)
+    plt.show()
+    return None
diff --git a/aircraftstudio/evaluator/inertia.py b/aircraftstudio/evaluator/inertia.py
new file mode 100644
index 0000000..f047766
--- /dev/null
+++ b/aircraftstudio/evaluator/inertia.py
@@ -0,0 +1,66 @@
+def get_centroid(aircraft):
+    """Return the coordinates of the centroid."""
+    # stringer_area = aircraft.wing.stringers.area
+    # cap_area = aircraft.wing.spars.cap_area
+
+    # TODO: Fix this
+    # caps_x = [value for spar in aircraft.wing.spars.x for value in spar]
+    # caps_z = [value for spar in aircraft.wing.spars.z for value in spar]
+    # stringers_x = aircraft.wing.stringers.x
+    # stringers_z = aircraft.wing.stringers.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)
+    return (200, 420)
+
+
+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)
diff --git a/aircraftstudio/evaluator/lift.py b/aircraftstudio/evaluator/lift.py
new file mode 100644
index 0000000..516d649
--- /dev/null
+++ b/aircraftstudio/evaluator/lift.py
@@ -0,0 +1,30 @@
+import numpy as np
+from math import sqrt
+
+
+def _get_lift_rectangular(aircraft, lift=50):
+    L_prime = np.array([
+        lift / (aircraft.wing.semi_span * 2)
+        for _ in range(aircraft.wing.semi_span)
+    ])
+    return L_prime
+
+
+def _get_lift_elliptical(aircraft, L_0=3.2):
+    L_prime = np.array([
+        0.5 * L_0 / (aircraft.wing.semi_span * 2) *
+        sqrt(1 - (y / aircraft.wing.semi_span)**2)
+        for y in range(aircraft.wing.semi_span)
+    ])
+    return L_prime
+
+
+def get_lift_total(aircraft):
+    """Combination of rectangular and elliptical lift."""
+    # F_z = self._get_lift_rectangular(aircraft) + self._get_lift_elliptical(
+    #     aircraft)
+    # F_z = self._get_lift_rectangular(
+    #     aircraft) + self._get_lift_elliptical(aircraft) / 2
+    # F_z = [i + j for i, j in self._get_lift_rectangular]
+    # return F_z
+    return 400
diff --git a/aircraftstudio/evaluator/mass.py b/aircraftstudio/evaluator/mass.py
new file mode 100644
index 0000000..7edb926
--- /dev/null
+++ b/aircraftstudio/evaluator/mass.py
@@ -0,0 +1,8 @@
+def get_mass_distribution(self, total_mass):
+    F_z = [total_mass / self.semi_span for x in range(0, self.semi_span)]
+    return F_z
+
+
+def get_mass_total(aircraft):
+    """Get the total aircraft mass."""
+    return 2000
diff --git a/aircraftstudio/generator/__init__.py b/aircraftstudio/generator/__init__.py
new file mode 100644
index 0000000..4f233cb
--- /dev/null
+++ b/aircraftstudio/generator/__init__.py
@@ -0,0 +1 @@
+from .generator import *
diff --git a/aircraftstudio/generator/generator.py b/aircraftstudio/generator/generator.py
new file mode 100644
index 0000000..898683a
--- /dev/null
+++ b/aircraftstudio/generator/generator.py
@@ -0,0 +1,43 @@
+"""
+The generator.py module contains classes describing genetic populations
+and methods to generate default aircraft.
+"""
+
+from aircraftstudio import creator
+
+
+def default_fuselage():
+    pass
+
+
+def default_propulsion():
+    pass
+
+
+class Population():
+    """Represents a collection of aircraft."""
+    def __init__(self, size):
+        self.aircrafts = []
+        for _ in range(size):
+            self.aircrafts.append(creator.base.Aircraft.from_random())
+        self.size = size
+        self.results = None
+        self.gen_number = 0  # incremented for every generation
+
+    #TODO class methods for default and random population
+    # def from_default(self, size):
+    #     for i in range(size):
+    #         self.aircrafts.append(creator.base.Aircraft.from_default())
+
+    # def from_random(self, size):
+    #     for i in range(size):
+    #         self.aircrafts.append(creator.base.Aircraft.from_random())
+
+    def mutate(self, prob_mt):
+        """Randomly mutate the genes of prob_mt % of the population."""
+    def crossover(self, prob_cx):
+        """Combine the genes of prob_cx % of the population."""
+    def reproduce(self, prob_rp):
+        """Pass on the genes of the fittest prob_rp % of the population."""
+    def fitness():
+        """Rate the fitness of an individual on a relative scale (0-100)"""
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