Returns the approximate maximum flexural wavelength
    This is important when padding of the grid is required: in Flexure (this 
    code), grids are padded out to one maximum flexural wavelength, but in any 
    case, the flexural wavelength is a good characteristic distance for any 
    truncation limit

def calc_max_flexural_wavelength(self):
    """
    Returns the approximate maximum flexural wavelength
    This is important when padding of the grid is required: in Flexure (this 
    code), grids are padded out to one maximum flexural wavelength, but in any 
    case, the flexural wavelength is a good characteristic distance for any 
    truncation limit
    """
    if np.isscalar(self.D):
      Dmax = self.D
    else:
      Dmax = self.D.max()
    # This is an approximation if there is fill that evolves with iterations 
    # (e.g., water), but should be good enough that this won't do much to it
    alpha = (4*Dmax/(self.drho*self.g))**.25 # 2D flexural parameter
    self.maxFlexuralWavelength = 2*np.pi*alpha
    self.maxFlexuralWavelength_ncells_x = int(np.ceil(self.maxFlexuralWavelength / self.dx))
    self.maxFlexuralWavelength_ncells_y = int(np.ceil(self.maxFlexuralWavelength / self.dy))