wecopttool.core.WEC

class WEC

A wave energy converter (WEC) object for performing simulations using the pseudo-spectral solution method.

To create the WEC use one of the initialization methods:

• wecopttool.WEC.__init__()

• wecopttool.WEC.from_bem()

• wecopttool.WEC.from_floating_body()

• wecopttool.WEC.from_impedance().

Note

Direct initialization of a wecopttool.WEC object as WEC(f1, nfreq, forces, ...) using wecopttool.WEC.__init__() is discouraged. Instead use one of the other initialization methods listed in the See Also section.

To solve the pseudo-spectral problem use wecopttool.WEC.solve().

__init__(f1, nfreq, forces, constraints=None, inertia_matrix=None, ndof=None, inertia_in_forces=False, dof_names=None)

Create a WEC object directly from its inertia matrix and list of forces.

The wecopttool.WEC class describes a WEC’s equation of motion as \(ma=Σf\) where the inertia_matrix matrix specifies the inertia \(m\), and the forces dictionary specifies the different forces to be summed. The forces can be linear or nonlinear. If inertia_in_forces is True the equation of motion is \(Σf=0\), which is included to allow for initialization using an intrinsic impedance through the WEC.from_impedance initialization function.

Note

Direct initialization of a wecopttool.WEC object as WEC(f1, nfreq, forces, ...) is discouraged. Instead use one of the other initialization methods listed in the See Also section.

Parameters:

• f1 (float) – Fundamental frequency f1 [\(Hz\)].

• nfreq (int) – Number of frequencies (not including zero frequency), i.e., freqs = [0, f1, 2*f1, ..., nfreq*f1].

• forces (Mapping[str, StateFunction]) – Dictionary with entries {'force_name': fun}, where fun has a signature def fun(wec, x_wec, x_opt, waves):, and returns forces in the time-domain of size (2*nfreq+1, ndof).

• constraints (Iterable[Mapping] | None) – List of constraints, see documentation for scipy.optimize.minimize() for description and options of constraints dictionaries. If None: empty list [].

• inertia_matrix (ndarray | None) – Inertia matrix of size (ndof, ndof). Not used if inertia_in_forces is True.

• ndof (int | None) – Number of degrees of freedom. Must be specified if inertia_in_forces is True, else not used.

• inertia_in_forces (bool | None) – Set to True if inertial “forces” are included in the forces argument. This scenario is rare. If using an intrinsic impedance, consider initializing with wecoptool.core.WEC.from_impedance() instead.

• dof_names (Iterable[str] | None) – Names of the different degrees of freedom (e.g. 'Heave'). If None the names ['DOF_0', ..., 'DOF_N'] are used.

Raises:

• ValueError – If inertia_in_forces is True but ndof is not specified.

• ValueError – If inertia_in_forces is False but inertia_matrix is not specified.

• ValueError – If inertia_matrix does not have the correct size ((ndof, ndof)).

• ValueError – If dof_names does not have the correct size (ndof).

Return type:

None

See also

from_bem

Initialize a wecopttool.WEC object from BEM results.

from_floating_body

Initialize a wecopttool.WEC object from a capytaine.bodies.bodies.FloatingBody object.

from_impedance

Initialize a wecopttool.WEC object from an intrinsic impedance array and excitation coefficients.

Attributes

WEC.constraints	List of constraints.
WEC.derivative2_mat	Matrix to create Fourier coefficients of the second derivative of some quantity.
WEC.derivative_mat	Matrix to create Fourier coefficients of the derivative of some quantity.
WEC.dof_names	Names of the different degrees of freedom.
WEC.dt	Time spacing [s].
WEC.f1	Fundamental frequency f1 [\(Hz\)].
WEC.forces	Dictionary of forces.
WEC.frequency	Frequency vector [\(Hz\)].
WEC.inertia	Function representing the inertial term \(ma\) in the WEC's dynamics equation.
WEC.inertia_in_forces	Whether inertial "forces" are included in the forces dictionary.
WEC.inertia_matrix	Inertia (mass) matrix.
WEC.ncomponents	Number of Fourier components (2*nfreq) for each degree of freedom.
WEC.ndof	Number of degrees of freedom.
WEC.nfreq	Number of frequencies, not including the zero-frequency.
WEC.nstate_wec	Length of the WEC dynamics state vector consisting of the Fourier coefficient of the position of each degree of freedom.
WEC.nt	Number of timesteps.
WEC.omega	Radial frequency vector [rad/s].
WEC.period	Period vector [s].
WEC.tf	Final time (repeat period) [s].
WEC.time	Time vector [s], size '(2*nfreq, ndof)', not containing the end time 'tf'.
WEC.time_mat	Matrix to create time-series from Fourier coefficients.
WEC.w1	Fundamental radial frequency [rad/s].

Methods

decompose_state	Split the state vector into the WEC dynamics state and the optimization (control) state.
dofmat_to_vec	Flatten a matrix to a vector.
fd_to_td	Convert a frequency-domain array to time-domain.
from_bem	Create a WEC object from linear hydrodynamic coefficients obtained using the boundary element method (BEM) code Capytaine.
from_floating_body	Create a WEC object from a Capytaine FloatingBody (:py:class:capytaine.bodies.bodies.FloatingBody).
from_impedance	Create a WEC object from the intrinsic impedance and excitation coefficients.
post_process	Post-process the results from wecopttool.WEC.solve().
residual	Return the residual of the dynamic equation (r = m⋅a-Σf).
solve	Simulate WEC dynamics using a pseudo-spectral solution method and returns the raw results dictionary produced by scipy.optimize.minimize().
td_to_fd	Convert a time-domain array to frequency-domain.
time_mat_nsubsteps	Create a time matrix similar to wecopttool.WEC.time_mat() but with finer time-domain discretization.
time_nsubsteps	Create a time vector with finer discretization.
vec_to_dofmat	Convert a vector to a matrix with one column per degree of freedom.