(in progress) commercial sizing model

gpkitmodels/aircraft/d8.py

@@ -0,0 +1,68 @@
+"""Commercial Aircraft Model loosely inspired by TASOPT"""
+import numpy as np
+from gpkit import Variable, Model, units
+
+
+rho = Variable("\\rho", 0.4, "kg/m^3", "air density")
+
+
+class Wing(Model):
+    def __init__(self, **kwargs):
+        e = Variable("e", 0.85, "-",
+                     "Oswald efficiency, should come from aircraft wing")
+        S = Variable("S", 1300, "ft^2", "wing area")
+        A = Variable("A", 9.45, "-", "Aspect ratio")
+        W = Variable("W", 1, "lbf", "weight")
+        b = Variable("b", "ft", "wing span")
+        CD = Variable("C_D", "-", "drag coefficient")
+        CL = Variable("C_L", "-", "lift coefficient")
+
+        self.unused_variables = [W]
+        Model.__init__(self, None, [b**2 == S/A,
+                                    CD >= 0.02 + CL**2/np.pi/e/A,
+                                    W == W])
+
+
+class SteadyFlight(Model):
+    def __init__(self, **kwargs):
+        CL = Variable("C_L", "-", "lift coefficient")
+        CD = Variable("C_D", "-", "drag coefficient")
+        V = Variable("V", 200, "knots", "true airspeed")
+        T = Variable("T", "lbf", "thrust")
+        L = Variable("L", "lbf", "lift")
+        Sref = Variable("S_{ref}", "ft^2", "reference area")
+        Wfuel = Variable("W_{fuel}", 36864.9, "lbf", "fuel weight")
+        Wref = Variable("W_{ref}", "lbf", "dry mission weight")
+        W = Variable("W", "lbf", "total weight")
+
+        constraints = [L <= 0.5*rho*V**2*CL*Sref,
+                       T >= 0.5*rho*V**2*CD*Sref,
+                       W >= Wref + Wfuel,
+                       W <= L,
+                       ]
+
+        Model.__init__(self, None, constraints, **kwargs)
+
+
+class CommercialAircraft(Model):
+    def __init__(self, **kwargs):
+        W_e = Variable("W_e", 84749.8, "lbf", "empty weight")
+        Wpay = Variable("W_{pay}", 38700, "lbf", "payload weight")
+        W = Variable("W", "lbf", "total weight")
+
+        wing = Wing()
+        constraints = [wing]
+
+        sf = SteadyFlight()
+        sf.subinplace({sf["S_{ref}"]: wing["S"],
+                       sf["C_L"]: wing["C_L"],
+                       sf["C_D"]: wing["C_D"]})
+        constraints.append(sf)
+        constraints.append(sf["W_{ref}"] >= W_e + Wpay + wing["W"])
+
+        Model.__init__(self, sf["T"], constraints, **kwargs)
+
+
+m = CommercialAircraft()
+sol = m.solve(verbosity=0)
+print sol.table()