def calculate_viscous_effects(self, S_wave):
"""
Calculate viscous forces and damping with the given wave spectrum.
Note that this can be iterative, as the transfer functions will be
re-calculated using previously-calculated viscous effects.
"""
assert len(S_wave) == len(self.w)
H_wave = self.transfer_function_from_wave_elevation()
self.Bv, self.Fvc, self.Fvv = self.morison.total_drag(self.w, H_wave,
S_wave)
# Fvv is the actual force/unit wave height at each wave
# frequency -- to get the spectrum, it's like the first-order
# wave force spectrum.
self.viscous_force_spectrum = response_spectrum(self.Fvv, S_wave)
def response_spectrum(self, S_wave, second_order=True, viscous=True):
"""Convenience method which calculates the response spectrum
"""
S1 = self.hydro_info.first_order_force_spectrum(self.w, S_wave)
if second_order:
S2 = self.hydro_info.second_order_force_spectrum(self.w, S_wave)
else:
S2 = zeros_like(S1)
if viscous:
self.calculate_viscous_effects(S_wave)
Sv = self.viscous_force_spectrum
else:
Sv = zeros_like(S1)
self.calculate_wave_drift_damping(S_wave)
# XXX this doesn't work well if second_order or viscous is set
# to False -- transfer_function() will use previously-calculated values
H = self.transfer_function()
SF = S1 + S2 + Sv
Sx = response_spectrum(H[:, :, :6], SF)
return Sx
def first_order_force_spectrum(self, w, S_wave, heading=0):
# Interpolate complex wave excitation force
X = self.X(w, heading)
return response_spectrum(X, S_wave)
def first_order_force_spectrum(self, w, S_wave, heading=0):
# Interpolate complex wave excitation force
X = self.X(w, heading)
return response_spectrum(X, S_wave)
