added new cd0 calculator

Model/Propulsion/cruise_comp.py

@@ -8,16 +8,17 @@ class   CruiseComp(ExplicitComponent):
 
     def setup(self):
         self.add_input('W',desc='Weight of aircraft')
-        self.add_input('Cd',desc='coefficient of drag')
-        self.add_input('Cl',desc='coefficient of lift')
+        #self.add_input('Cd',desc='coefficient of drag')
+        #self.add_input('Cl',desc='coefficient of lift')
         self.add_input('AR',desc='Aspect Ratio')
         self.add_input('S',desc='Refernce Area')
         self.add_input('V',desc='Airspeed')
-        self.add_input('cd0',desc='zero lift drag')
+        #self.add_input('cd0',desc='zero lift drag')
 
         self.add_output('P_C',desc='Power required for cruise')
         self.add_output('cl')
         self.add_output('cd')
+        self.add_output('cd0')
         self.declare_partials(of='*', wrt='*', method='cs')
 
 
@@ -26,10 +27,17 @@ def compute(self,inputs,outputs):
         W = inputs['W']*9.81
         # add Cl & Cd if airfoil code doesnt work
         cl = 2*W/(rho*(inputs['V']**2)*inputs['S'])
-
+        a = -2.5529
+        b = 1
+        c = 0.8635
+        d = 0.5632
+        Swet = (10**c)*(inputs['W']*2.2046)**d
+        f = (10**a)*Swet**b
+        cd0 = f/(inputs['S']*10.7639)
         k = 1/(3.14*0.8*inputs['AR']) # e = 0.8
-        cd = inputs['cd0'] + k*cl**2
+        cd = cd0 + k*cl**2
         outputs['cl'] = cl
         outputs['cd'] = cd
+        outputs['cd0'] = cd0
         #outputs['P_C'] = (( (2*(W**3)*(inputs['Cd']**2))/(inputs['S']*rho*(inputs['Cl']**3)) )**.5)/1000
         outputs['P_C'] = (( (2*(W**3)*(cd**2))/(inputs['S']*rho*(cl**3) ))**.5)/1000

solver.py

@@ -20,12 +20,12 @@
 ivc.add_output('m')
 ivc.add_output('r')
 ivc.add_output('TS',val=188) # ~50% of mach @ Sl
-ivc.add_output('cd0',val=0.0197)
+#ivc.add_output('cd0',val=0.0197)
 ivc.add_output('rho',val=1.225)
 
 ivc.add_output('V') 
-ivc.add_output('Cd',val=0.03)
-ivc.add_output('Cl',val=0.32)
+#ivc.add_output('Cd',val=0.03)
+#ivc.add_output('Cl',val=0.32)
 ivc.add_output('S',val=13.2)
 ivc.add_output('AR',val=7)
 
@@ -71,19 +71,19 @@
 
 # connecting to Props comp
 model.connect('weight.W0','FOM.W')
-model.connect('cd0','FOM.cd0')
+model.connect('cruiseP.cd0','FOM.cd0')
 model.connect('rho','FOM.rho')
 model.connect('TS','FOM.TS')
 model.connect('r','FOM.r')
 
 # connecting to cruise power comp
 model.connect('weight.W0','cruiseP.W')
-model.connect('Cd','cruiseP.Cd')
-model.connect('Cl','cruiseP.Cl')
+#model.connect('Cd','cruiseP.Cd')
+#model.connect('Cl','cruiseP.Cl')
 model.connect('AR','cruiseP.AR')
 model.connect('S','cruiseP.S')
 model.connect('V','cruiseP.V')
-model.connect('cd0','cruiseP.cd0')
+#model.connect('cd0','cruiseP.cd0')
 
 # connecting to range comp
 model.connect('Wb','range.B_W')
@@ -143,4 +143,5 @@
 print('Max Trip Range @',prob['V'],'[m/s]:',prob['range.R'],'[km]','Time',prob['range.t'],'[hr]')
 print('cl',prob['cruiseP.cl'])
 print('cd',prob['cruiseP.cd'])
+print('cd0',prob['cruiseP.cd0'])