Change order of parameters in v_wind_hellman() for consistency

Author: SabineHaas

windpowerlib/modelchain.py

@@ -260,7 +260,7 @@ def v_wind_hub(self, weather, data_height):
             v_wind = wind_speed.v_wind_hellman(
                 weather['v_wind'], data_height['v_wind'],
                 self.wind_turbine.hub_height,
-                self.hellman_exp, weather['z0'])
+                weather['z0'], self.hellman_exp)
         else:
             raise ValueError("'{0}' is an invalid value.".format(
                              self.wind_model) + "`wind_model` " +

windpowerlib/wind_speed.py

@@ -82,8 +82,8 @@ def logarithmic_wind_profile(v_wind, v_wind_height, hub_height, z_0,
             np.log((v_wind_height - 0.7 * obstacle_height) / z_0))
 
 
-def v_wind_hellman(v_wind, v_wind_height, hub_height, hellman_exp=None,
-                   z_0=None):
+def v_wind_hellman(v_wind, v_wind_height, hub_height, z_0=None,
+                   hellman_exp=None):
     r"""
     Calculates the wind speed at hub height using the hellman equation.
 
@@ -99,14 +99,14 @@ def v_wind_hellman(v_wind, v_wind_height, hub_height, hellman_exp=None,
         Height for which the parameter `v_wind` applies.
     hub_height : float
         Hub height of wind turbine.
+    z_0 : pandas.Series or numpy.array or float
+        Roughness length. Default: None. If given and `hellman_exp` is None:
+        `hellman_exp` = 1 / ln(h_hub/z_0), otherwise `hellman_exp` = 1/7.
     hellman_exp : float
         The Hellman exponent, which combines the increase in wind speed due to
         stability of atmospheric conditions and surface roughness into one
         constant. Default: None. If None and roughness length is given
         `hellman_exp` = 1 / ln(h_hub/z_0), otherwise `hellman_exp` = 1/7.
-    z_0 : pandas.Series or numpy.array or float
-        Roughness length. Default: None. If given
-        `hellman_exp` = 1 / ln(h_hub/z_0), otherwise `hellman_exp` = 1/7.
 
     Returns
     -------