allow for different polar fitted data (#136)

* allow for any airfoil data

* add tau as independent var if fit has d=3

gpkitmodels/GP/aircraft/wing/wing.py

@@ -61,7 +61,7 @@ def setup(self, N):
 
 class WingAero(Model):
     "wing aerodynamic model with profile and induced drag"
-    def setup(self, static, state):
+    def setup(self, static, state, fitdata="jho_fitdata.csv"):
         "wing drag model"
         Cd = Variable("C_d", "-", "wing drag coefficient")
         CL = Variable("C_L", "-", "lift coefficient")
@@ -70,15 +70,20 @@ def setup(self, static, state):
         Re = Variable("Re", "-", "Reynold's number")
         cdp = Variable("c_{dp}", "-", "wing profile drag coeff")
 
-        path = os.path.dirname(__file__)
-        df = pd.read_csv(path + os.sep + "jho_fitdata.csv")
+        path = os.path.dirname(os.path.abspath(fitdata))
+        df = pd.read_csv(path + os.sep + fitdata)
         fd = df.to_dict(orient="records")[0]
 
+        if fd["d"] == 2:
+            independentvars = [CL, Re]
+        elif fd["d"] == 3:
+            independentvars = [CL, Re, static["\\tau"]]
+
         constraints = [
             Cd >= cdp + CL**2/np.pi/static["AR"]/e,
             Re == state["\\rho"]*state["V"]*static["c_{MAC}"]/state["\\mu"],
             # XfoilFit(fd, cdp, [CL, Re], airfoil="jho1.dat"),
-            XfoilFit(fd, cdp, [CL, Re]),
+            XfoilFit(fd, cdp, independentvars),
             CL <= CLstall
             ]