capytaine.bodies.bodies module

Floating bodies to be used in radiation-diffraction problems.

class capytaine.bodies.bodies.FloatingBody(mesh=None, dofs=None, mass=None, center_of_mass=None, name=None, *, lid_mesh=None)

Bases: _HydrostaticsMixin, ClippableMixin, Abstract3DObject

A floating body described as a mesh and some degrees of freedom.

The mesh structure is stored as a Mesh from capytaine.mesh.mesh or a CollectionOfMeshes from capytaine.mesh.meshes_collection.

The degrees of freedom (dofs) are stored as a dict associating a name to a complex-valued array of shape (nb_faces, 3). To each face of the body (as indexed in the mesh) corresponds a complex-valued 3d vector, which defines the displacement of the center of the face in frequency domain.

Parameters:

• mesh (MeshLike, optional) – the mesh describing the geometry of the hull of the floating body. If none is given, a empty one is created.

• lid_mesh (MeshLike or None, optional) – a mesh of an internal lid for irregular frequencies removal. Unlike the mesh of the hull, no dof is defined on the lid_mesh. If none is given, none is used when solving the Boundary Integral Equation.

• dofs (dict, optional) – the degrees of freedom of the body. If none is given, a empty dictionary is initialized.

• mass (float or None, optional) – the mass of the body in kilograms. Required only for some hydrostatics computation. If None, the mass is implicitly assumed to be the mass of displaced water.

• center_of_mass (3-element array, optional) – the position of the center of mass. Required only for some hydrostatics computation.

• name (str, optional) – a name for the body. If none is given, the one of the mesh is used.

add_all_rigid_body_dofs() → None

Add the six degrees of freedom of rigid bodies (in place).

add_dofs_labels_to_matrix(matrix)

Helper function turning a bare matrix into a matrix labelled by the name of the dofs of the body, to be used for instance for the computation of RAO.

add_dofs_labels_to_vector(vector)

Helper function turning a bare vector into a vector labelled by the name of the dofs of the body, to be used for instance for the computation of RAO.

add_rotation_dof(axis=None, name=None, amplitude=1.0) → None

Add a new rotation dof (in place). If no axis is given, the code tries to infer it from the name.

Parameters:

• axis (Axis, optional) – the axis of the rotation

• name (str, optional) – a name for the degree of freedom

• amplitude (float, optional) – amplitude of the dof (default: 1.0)

add_translation_dof(direction=None, name=None, amplitude=1.0) → None

Add a new translation dof (in place). If no direction is given, the code tries to infer it from the name.

Parameters:

• direction (array of shape (3,), optional) – the direction of the translation

• name (str, optional) – a name for the degree of freedom

• amplitude (float, optional) – amplitude of the dof (default: 1.0 m/s)

animate(motion, *args, **kwargs)

Display a motion as a 3D animation.

Parameters:

motion (dict or pd.Series or str) – A dict or series mapping the name of the dofs to its amplitude. If a single string is passed, it is assumed to be the name of a dof and this dof with a unit amplitude will be displayed.

assemble_arbitrary_array(locations: ndarray)

assemble_regular_array(distance, nb_bodies)

Create an regular array of identical bodies.

Parameters:

• distance (float) – Center-to-center distance between objects in the array

• nb_bodies (couple of ints) – Number of objects in the x and y directions.

Return type:

FloatingBody

clip(*args, inplace=True, name=None, **kwargs)

static combine_dofs(bodies) → dict

Combine the degrees of freedom of several bodies.

copy(name=None) → FloatingBody

Return a deep copy of the body.

Parameters:

name (str, optional) – a name for the new copy

extract_faces(id_faces_to_extract, return_index=False)

Create a new FloatingBody by extracting some faces from the mesh. The dofs evolve accordingly. The lid_mesh, center_of_mass, mass and hydrostatics data are discarded.

first_irregular_frequency_estimate(*, g=9.81)

Estimates the angular frequency of the lowest irregular frequency. This is based on the formula for the lowest irregular frequency of a parallelepiped of size \(L \times B\) and draft \(H\):

(11)\[\omega = \sqrt{ \frac{\pi g \sqrt{\frac{1}{B^2} + \frac{1}{L^2}}} {\tanh\left(\pi H \sqrt{\frac{1}{B^2} + \frac{1}{L^2}} \right)} }\]

The formula is applied to all shapes to get an estimate that is usually conservative. The definition of a lid (supposed to be fully covering and horizontal) is taken into account.

static from_file(filename: str, file_format=None, name=None) → FloatingBody

Create a FloatingBody from a mesh file using meshmagick. Kinda deprecated, use cpt.load_mesh instead.

static from_meshio(mesh, name=None) → FloatingBody

Create a FloatingBody from a meshio mesh object. Kinda deprecated, use cpt.load_mesh instead.

integrate_pressure(pressure)

join_bodies(*, name=None) → FloatingBody

keep_only_dofs(*args, inplace=True, name=None, **kwargs)

property minimal_computable_wavelength

For accuracy of the resolution, wavelength should not be smaller than this value.

mirror(*args, inplace=True, name=None, **kwargs)

property nb_dofs: int

Number of degrees of freedom.

rotate(*args, inplace=True, name=None, **kwargs)

show(**kwargs)

show_matplotlib(*args, **kwargs)

translate(*args, inplace=True, name=None, **kwargs)