migflow.scontact

Model for Immersed Granular Flow: Fluid user interface

Contact: jonathan.lambrechts@uclouvain.be Webpage: www.migflow.be

MigFlow computes immersed granular flows using an unresolved FEM-DEM model. The continuous phase (mixture) is computed by solving averaged Navier-Stokes equations on unstructured meshes with the continuous finite element method.

class migflow.scontact.ParticleProblem(dim)

Bases: object

Creates the numerical structure containing all the physical particles that appear in the problem

Builds the particle problem structure.

Parameters

dim (int) – Dimension of the problem

Raises

  • ValueError – If the dimension differs from 2 or 3

  • NameError – If C builder cannot be found

__del__()

Deletes the particle solver structure.

add_body(x, invertM, invertI)

Adds a body in the particle problem. — Only in 2D

Parameters

  • x (ndarray) – array of the position of the body

  • InvertM – inverse mass of the body

  • InvertI – inverse inertia of the body

Returns

body id

Return type

int

add_boundary_periodic_entity(dim, transform)

Adds a periodic entity.

Parameters

  • dim (int) – dimension of the entity

  • transform (ndarray) – array of the transformation to applied to the periodic entity

add_boundary_periodic_point(x, tag)

Adds a boundary periodic point.

Parameters

  • x (ndarray) – array of the coordinates of the point

  • tag (int) – entity tag

add_boundary_periodic_segment(x0, x1, tag)

Adds a boundary periodic segment.

Parameters

  • x0 (ndarray) – array of the coordinates of the first endpoint

  • x1 (ndarray) – array of the coordinates of the second endpoint

  • tag (int) – entity tag

add_boundary_periodic_triangle(x0, x1, x2, tag)

Adds a boundary periodic triangle.

Parameters

  • x0 (ndarray) – array of the coordinates of the first summit

  • x1 (ndarray) – array of the coordinates of the second summit

  • x2 (ndarray) – array of the coordinates of the third summit

  • tag (int) – tag of the periodic entity

add_boundary_segment(x0, x1, tag, material='default')

Adds a boundary segment.

Parameters

  • x0 (ndarray) – array of the coordinates of the first endpoint

  • x1 (ndarray) – array of the coordinates of the second endpoint

  • tag (str) – segment tag

  • material (str) – segment material

add_boundary_triangle(x0, x1, x2, tag, material='default')

Adds a boundary triangle.

Parameters

  • x0 (ndarray) – array of the coordinates of the first summit

  • x1 (ndarray) – array of the coordinates of the second summit

  • x2 (ndarray) – array of the coordinates of the third summit

  • tag (str) – triangle tag

  • material (str) – triangle material

add_entities(xbody, invertM=0.0, invertI=0.0, particles_coordinates=None, particles_radius=None, particles_materials='default', segments_coordinates=None, segments_tags=None, segments_materials='default', triangles_coordinates=None, triangles_tags=None, triangles_materials='default', is_relative_position=True)

Adds entities (either particles, segments or triangles) to a body described by its position, inverse of mass and inverse of inertia.

Parameters

  • xbody (np.ndarray) – position of the body

  • invertM (float, optional) – inverse mass of the body. Defaults to 0.

  • invertI (float, optional) – inverse inertia of the body. Defaults to 0.

  • particles_coordinates (np.ndarray, optional) – position of the particles. Defaults to None.

  • particles_radius (Union[np.ndarray, float], optional) – array of the particles radii. Defaults to None.

  • particles_materials (Union[str, List[str]], optional) – array of the particles material. Defaults to “default”.

  • segments_coordinates (np.ndarray, optional) – array of the segments coordinates as n_segments x 2 x dimension. Defaults to None.

  • segments_tags (Union[str, List[str]], optional) – array of the segments tags. Defaults to None.

  • segments_materials (Union[str, List[str]], optional) – array of the segments materials. Defaults to “default”.

  • triangles_coordinates (np.ndarray, optional) – array of the segments coordinates as n_segments x 3 x dimension. Defaults to None.

  • triangles_tags (str, optional) – array of the triangles tags. Defaults to None.

  • triangles_materials (Union[str, List[str]], optional) – array of the triangles materials. Defaults to “default”.

  • is_relative_position (bool, optional) – flag if the given position is the relative position towards the body or the absolute position. Defaults to True.

Returns

body id

Return type

int

add_particle(x, r, m, tag='default', forced=False, inverse_inertia=None)

Adds a particle in the particle container.

Parameters

  • x (ndarray) – array of the particle position

  • r (float) – particle radius

  • m (float) – particle mass

  • tag (str) – particle material

Returns

body id

Return type

int

add_particle_body(positions, radii, masses, material='default', forced=False)

Adds a body in the particle problem with a list of constituting particles — Only in 2D

Parameters

  • positions (ndarray) – positions of the particles constituting the body

  • radii (ndarray) – radii of the particles

  • masses (ndarray) – masses of the particles

  • material (str) – material of the particles

  • forced (bool) – Flag indicating whether the body is forced or not

Returns

body id

Return type

int

add_particle_to_body(x, r, body, material='default')

Adds a particle to a body.

Parameters

  • x (ndarray) – array of the particle positon with respect to the body’s centre of mass

  • r (float) – Particle radius

  • body (int) – number of the body to which the particle will be added

  • material (str) – Particle material

add_particles(x, r, m, tag='default', forced=False, inverse_inertia=None)

Adds particles in the particle container.

Parameters

  • x (ndarray) – array of tuple to set the centre particle position

  • r (ndarray) – array of particle radius

  • m (ndarray) – array of particle mass

  • tag (str) – particle material

Returns

id of the added bodies

Return type

np.ndarray

add_segment_to_body(x0, x1, body, tag, material='default')

Adds a segment to a body.

Parameters

  • x0 (np.ndarray) – array of the coordinates of the first endpoint

  • x1 (np.ndarray) – array of the coordinates of the second endpoint

  • body (int) – body id

  • tag (str) – boundary id associated to the segment

  • material (str) – Segment material

add_triangle_to_body(x0, x1, x2, body, tag, material='default')

Adds a segment to a body.

Parameters

  • x0 (np.ndarray) – array of the coordinates of the first endpoint

  • x1 (np.ndarray) – array of the coordinates of the second endpoint

  • body (int) – body id

  • tag (str) – boundary id associated to the segment

  • material (str) – Segment material

body_constraint()

Returns the invert mases of the bodies. :returns: Array of the body invert masses :rtype: np.ndarray

body_invert_inertia()

Returns the invert inertias of the bodies. :returns: Array of the body invert inertias :rtype: np.ndarray

body_invert_mass()

Returns the invert mases of the bodies. :returns: Array of the body invert masses :rtype: np.ndarray

body_omega()

Returns the angular velocities of the bodies. :returns: Array of the body angular velocities :rtype: np.ndarray

body_position()

Returns the positions of the bodies. :returns: Array of the body positions :rtype: np.ndarray

body_theta()

Returns the array of the body angles. :returns: Array of the body angles :rtype: np.ndarray

body_velocity()

Returns the velocities of the bodies. :returns: Array of the body velocities :rtype: np.ndarray

bounding_box()

Returns the bounding box of the particle problem. :returns: position of the lower left corner, position of the upper right corner :rtype: Tuple[np.ndarray, np.ndarray]

compute_relative_position(mass_center, particles_position, theta)
compute_stress_tensor(nodes, radius)

Computes the stress tensor of the granular material :type nodes: ndarray :param nodes: Array of nodes at which to compute the stress tensor :param r: Radius within which the contact forces will be averaged

Returns

Array of stresses on the nodes of the grid

Return type

np.ndarray

contact_forces()

Returns the contact forces on each particle. :returns: Array of the particle contact forces :rtype: np.ndarray

contacts()

Gives the contacts between the bodies. :returns: Array of contact forces between the particles :rtype: np.ndarray

delassus()

Returns the delassus operators of the particles. :returns: Array of the particle delassus operators :rtype: np.ndarray

dim()

Returns the dimension of the particle problem. :returns: Dimension of the problem :rtype: int

get_boundary_forces(tag='default')

Returns the forces acting on a boundary because of the contacts in the global basis. :type tag: str :param tag: Name of the boundary

Returns

Array of forces on boundary named tag

Return type

np.ndarray

get_material_id(material)

Returns the number associated to a string material. :type material: str :param material: string material.

Returns

number associated to the string material

Return type

int

get_tag_id(tag='default')

Returns the number associated to a string tag. :type tag: str :param tag: string tag.

Returns

number associated to the string tag

Return type

int

id()

Returns the ids of the particles. :returns: Array of the particle ids :rtype: np.ndarray

init_body(reference_position, relative_position, particle_masses, particle_radii, material='default')
Return type

int

iterate(dt, forces, torques=None, body_forces=None, tol=1e-08, force_motion=0)
Computes iteratively the set of velocities that respect the non-interpenetration constrain.

Returns 1 if the computation converged, 0 otherwise.

Parameters

  • dt (float) – Numerical time step

  • forces (ndarray) – List of vectors containing the forces applied on the particles

  • body_forces (Optional[ndarray]) – List of forces applied to the bodies

  • tol (float) – Optional argument defining the interpenetration tolerance to stop the NLGS iterations of the NSCD

  • force_motion (int) – Optional argument allowing to move the grains if convergence has not been reached when set to 1

load_msh_boundaries(filename, tags=None, shift=None, material='default')

Loads the numerical domain and set the physical boundaries the particles cannot go through.

Parameters

  • filename (str) – name of the msh file. If None the current gmsh model is loaded without the need to a msh file.

  • tags (Optional[str]) – tags of physical boundary defined in the msh file

  • shift (Optional[ndarray]) – optional argument to shift the numerical domain

  • material (str) – material of the boundary

material()

Returns the materials of the particles. :returns: Array of the particle materials :rtype: np.ndarray

mu()

Returns the array of the friction coefficients between materials. :returns: Array of the friction coefficients between materials. :rtype: np.ndarray

n_bodies()

Returns the number of bodies. :returns: number of bodies :rtype: int

n_particles()

Returns the number of particles. :returns: number of particles :rtype: int

omega()

Returns the omega of the particles. :returns: Array of the particle omega :rtype: np.ndarray

parse_type(tname)
particle_body()

Returns the bodies associated to each particle

Returns

body id

Return type

np.ndarray

particle_relative_position()

Returns the relative positions of the particles

Returns

Array of the relative positions

Return type

np.ndarray

periodic_entity()

Returns the array of periodic entities. :returns: Array of periodic entities :rtype: np.ndarray

periodic_points()

Returns the array of periodic points. :returns: Array of periodic points :rtype: np.ndarray

periodic_segments()

Returns the array of periodic segments.

Return type

ndarray

periodic_triangles()

Returns the array of periodic triangles. :returns: Array of periodic segments :rtype: np.ndarray

position()

Returns the positions of the particles. :returns: Array of the particle positions :rtype: np.ndarray

r()

Returns the raddi of the particles. :returns: Array of the particle radii :rtype: np.ndarray

read_mig(odir, t=None, iteration=None)

Reads output files. :type odir: str :param odir: Directory in which to read the file :type t: Optional[float] :param t: Time at which to read the file :param iteration; iteration to read: :param -1 for last iteration:

remove_bodies_flag(flag)

Removes particles based on given flag. :type flag: ndarray :param flag: flag with the same size as the number of bodies, with 0 for bodies to be removed and 1 for bodies to be kept

restore_state()

Restores the saved state of the particle problem.

save_state()

Saves the current state of the particle problem.

segments()

Returns the array of boundary segments. :returns: Array of boundary segments :rtype: np.ndarray

set_boundary_velocity(tag, v)

Sets the velocity of a boundary to a given value. :type tag: str :param tag: Name of the boundary :type v: ndarray :param v: Velocity vector to be given to the boundary

set_compute_contact_forces(compute_contact_forces=1)

Enables the computation of the contact forces on each particle if 1 and disables it if 0.

set_fixed_contact_geometry(flag)

Sets the management of the contact geometry, either fixed (default) or changing each time the contact is solved.

Parameters

flag (bool) – True for fixed False for changing.

set_friction_coefficient(mu, mat0='default', mat1='default')

Sets the friction coefficient between two materials.

Parameters

  • mu (float) – Value of the friction coefficient

  • mat0 (str) – First material

  • mat1 (str) – Second material

set_predict_basis(flag)

Set the management of the contact geometry, if true, a contact basis estimation is used in the contact resolution

Parameters

flag (bool) – True for the estimation

set_use_queue(use_queue=1)

Enables the use of the queue if 1 and disables it if 0.

triangles()

Returns the array of boundary triangles. :returns: Array of boundary triangles :rtype: np.ndarray

velocity()

Returns the velocities of the particles. :returns: Array of the particle velocities :rtype: np.ndarray

volume()

Returns the volumes of the particles. :returns: Array of the particle volumes :rtype: np.ndarray

write_mig(output_dir, t, extra_fields={}, write_contacts=True)

Writes output files for post-visualization. :type output_dir: str :param output_dir: Directory in which to write the file (expected to end in “.mig”) :type t: float :param t: Time at which the simulation is :type extra_fields: Dict[str, ndarray] :param extra_fields: extra field as a dictionnary {name : values}

migflow.scontact.fastdeposit_2d(boundary, r, svgfilename=None)

Fast 2d deposit of particles in a simple domain. :type boundary: ndarray :param boundary: points describing the boundary (single loop counter-clockwise oriented, no holes). :type boundary: np.ndarray [n,2] :type r: ndarray :param r: radius of the particles. :type r: np.ndarray [m] :type svgfilename: Optional[str] :param svgfilename: if not None, a svg file is generated illustrating the algorithm

Returns

positions of the particles.

Return type

np.ndarray [m,2]