Add depth parameter (h) to RunupModel class

py_wave_runup/models.py

@@ -19,7 +19,7 @@ class RunupModel(metaclass=ABCMeta):
 
     doi = None
 
-    def __init__(self, Hs=None, Tp=None, beta=None, Lp=None, r=None):
+    def __init__(self, Hs=None, Tp=None, beta=None, Lp=None, h=None, r=None):
         """
         Args:
             Hs (:obj:`float` or :obj:`list`): Significant wave height. In order to
@@ -32,6 +32,8 @@ def __init__(self, Hs=None, Tp=None, beta=None, Lp=None, r=None):
                 Must be defined if ``Lp`` is not defined.
             Lp (:obj:`float` or :obj:`list`): Peak wave length
                 Must be definied if ``Tp`` is not defined.
+            h (:obj:`float` or :obj:`list`): Depth of wave measurement(s). If not 
+                given deep-water conditions are assumed.
             r (:obj:`float` or :obj:`list`): Hydraulic roughness length. Can be
                 approximated by :math:`r=2.5D_{50}`.
         """
@@ -40,6 +42,7 @@ def __init__(self, Hs=None, Tp=None, beta=None, Lp=None, r=None):
         self.Tp = Tp
         self.beta = beta
         self.Lp = Lp
+        self.h = h
         self.r = r
 
         # Ensure wave length or peak period is specified
@@ -55,10 +58,19 @@ def __init__(self, Hs=None, Tp=None, beta=None, Lp=None, r=None):
         # Calculate wave length if it hasn't been specified.
         if not Lp:
             self.Tp = np.atleast_1d(Tp)
-            self.Lp = 9.81 * (self.Tp ** 2) / 2 / np.pi
+            if self.h:
+                k = []
+                for T in self.Tp:
+                    k.append(_newtRaph(T,self.h))
+                self.Lp = (2*np.pi)/k
+            else:
+                self.Lp = 9.81 * (self.Tp ** 2) / 2 / np.pi
         else:
             self.Lp = np.atleast_1d(Lp)
-            self.Tp = np.sqrt(2 * np.pi * self.Lp / 9.81)
+            if self.h:
+                self.Tp = np.sqrt( (2*np.pi*self.Lp)/(9.81*np.tanh((2*np.pi*self.h)/self.Lp)) )
+            else:
+                self.Tp = np.sqrt(2 * np.pi * self.Lp / 9.81)
 
         # Ensure arrays are of the same size
         if len(set(x.size for x in [self.Hs, self.Tp, self.beta, self.Lp])) != 1:
@@ -75,6 +87,32 @@ def _return_one_or_array(self, val):
             return val.item()
         else:
             return val
+
+    def _newtRaph(self,T,h):
+
+        # Function to determine k from dispersion relation given period (T) and depth (h) using
+        # the Newton-Raphson method.
+
+        if not np.isnan(T):
+            L_not = (9.81*(T**2))/(2*np.pi)
+            k1 = (2*np.pi)/L_not
+
+            def fk(k):
+                return (((2*np.pi)/T)**2)-(9.81*k*np.tanh(k*h))
+            def f_prime_k(k):
+                return (-9.81*np.tanh(k*h))-(9.81*k*(1-(np.tanh(k*h)**2)))
+
+            k2 = 100
+            i = 0
+            while abs((k2-k1))/k1 > 0.01:
+                  i+=1
+                  if i!=1:
+                      k1=k2
+                  k2 = k1-(fk(k1)/f_prime_k(k1))
+        else:
+            k2 = np.nan
+
+        return k2
 
 
 class Stockdon2006(RunupModel):