Nodes reference

BallastSystem

The BallastSystemNode is a non-physical node that marks a groups of Tank nodes as being the ballast system of a vessel.

The BallastSystem node can interface with the ballast-solver to automatically determine a suitable ballast configuration.

The tank objects are created separately and only their references are assigned to this ballast-system object.
That is done using the .tanks property which is a list.
The parent if this node is the vessel that the tanks belong to. The parent of the ballast system is expected to be
a Frame or Rigidbody which can be ballasted (should not have a parent).

Tanks can be excluded from the ballast algorithms by adding their names to the 'frozen' list.

Typical use:
- create vessel
- create tanks
- create ballast system
- adds tanks to ballast system using ballast_system.tanks.append(tank node)
- set the draft: ballast_system.target_elevation = -5.0 # note, typically negative
- and solve the tank fills: ballast_system.solve_ballast

​

Property	Read-Only	Documentation
target_elevation		The target elevation of the parent of the ballast system.
cogx	Read-only	X position of combined CoG of all tank contents in the ballast-system. (global coordinate) [m]
cogy	Read-only	Y position of combined CoG of all tank contents in the ballast-system. (global coordinate) [m]
cogz	Read-only	Z position of combined CoG of all tank contents in the ballast-system. (global coordinate) [m]
cog	Read-only	Combined CoG of all tank contents in the ballast-system. (global coordinate) [m,m,m]
weight	Read-only	Total weight of all tank fillings in the ballast system [kN]

Beam

A LinearBeam models a FEM-like linear beam element.

A LinearBeam node connects two Axis elements

By definition the beam runs in the X-direction of the nodeA axis system. So it may be needed to create a
dedicated Axis element for the beam to control the orientation.

The beam is defined using the following properties:

*  EIy  - bending stiffness about y-axis
*  EIz  - bending stiffness about z-axis
*  GIp  - torsional stiffness about x-axis
*  EA   - axis stiffness in x-direction
*  L    - the un-stretched length of the beam
*  mass - mass of the beam in [mT]

The beam element is in rest if the nodeB axis system

1. has the same global orientation as the nodeA system
2. is at global position equal to the global position of local point (L,0,0) of the nodeA axis. (aka: the end of the beam)

The scene.new_linearbeam automatically creates a dedicated axis system for each end of the beam. The orientation of this axis-system
is determined as follows:

First the direction from nodeA to nodeB is determined: D
The axis of rotation is the cross-product of the unit x-axis and D    AXIS = ux x D
The angle of rotation is the angle between the nodeA x-axis and D
The rotation about the rotated X-axis is undefined.

​

Property	Read-Only	Documentation
n_segments		Number of segments used in beam [-]
EIy		E * Iyy : bending stiffness in the XZ plane [kN m2] E is the modulus of elasticity; for steel 190-210 GPa (10^6 kN/m2) Iyy is the cross section moment of inertia [m4]
EIz		E * Izz : bending stiffness in the XY plane [kN m2] E is the modulus of elasticity; for steel 190-210 GPa (10^6 kN/m2) Iyy is the cross section moment of inertia [m4]
GIp		G * Ipp : torsional stiffness about the X (length) axis [kN m2] G is the shear-modulus of elasticity; for steel 75-80 GPa (10^6 kN/m2) Ip is the cross section polar moment of inertia [m4]
EA		E * A : stiffness in the length direction [kN] E is the modulus of elasticity; for steel 190-210 GPa (10^6 kN/m2) A is the cross-section area in [m2]
tension_only		axial stiffness (EA) only applicable to tension [True/False]
mass		Mass of the beam in [mT]
L		Length of the beam in unloaded condition [m]
nodeA		The axis system that the A-end of the beam is connected to. The beam leaves this axis system along the X-axis
nodeB		The axis system that the B-end of the beam is connected to. The beam arrives at this axis system along the X-axis
moment_A	Read-only	Moment on beam at node A (kNm, kNm, kNm) , axis system of node A
moment_B	Read-only	Moment on beam at node B (kNm, kNm, kNm) , axis system of node B
tension	Read-only	Tension in the beam [kN], negative for compression tension is calculated at the midpoints of the beam segments.
torsion	Read-only	Torsion moment [kNm]. Positive if end B has a positive rotation about the x-axis of end A torsion is calculated at the midpoints of the beam segments.
X_nodes	Read-only	Returns the x-positions of the end nodes and internal nodes along the length of the beam [m]
X_midpoints	Read-only	X-positions of the beam centers measured along the length of the beam [m]
global_positions	Read-only	Global-positions of the end nodes and internal nodes [m,m,m]
global_orientations	Read-only	Global-orientations of the end nodes and internal nodes [deg,deg,deg]
bending	Read-only	Bending forces of the end nodes and internal nodes [0, kNm, kNm]

Buoyancy

Buoyancy provides a buoyancy force based on a buoyancy mesh. The mesh is triangulated and chopped at the instantaneous flat water surface. Buoyancy is applied as an upwards force that the center of buoyancy. The calculation of buoyancy is as accurate as the provided geometry.

There as no restrictions to the size or aspect ratio of the panels. It is excellent to model as box using 6 faces. Using smaller panels has a negative effect on performance.

The normals of the panels should point towards to water.

Property	Read-Only	Documentation
trimesh	Read-only	Reference to TriMeshSource object
cob	Read-only	GLOBAL position of the center of buoyancy [m,m,m] (global axis)
cob_local	Read-only	Position of the center of buoyancy [m,m,m] (local axis)
displacement	Read-only	Displaced volume of fluid [m^3]

Cable

A Cable represents a linear elastic wire running from a Poi or sheave to another Poi of sheave.

A cable has a un-stretched length [length] and a stiffness [EA] and may have a diameter [m]. The tension in the cable is calculated.

Intermediate pois or sheaves may be added.

- Pois are considered as sheaves with a zero diameter.
- Sheaves are considered sheaves with the given geometry. If defined then the diameter of the cable is considered when calculating the geometry. The cable runs over the sheave in the positive direction (right hand rule) as defined by the axis of the sheave.

For cables running over a sheave the friction in sideways direction is considered to be infinite. The geometry is calculated such that the
cable section between sheaves is perpendicular to the vector from the axis of the sheave to the point where the cable leaves the sheave.

This assumption results in undefined behaviour when the axis of the sheave is parallel to the cable direction.

Notes:
    If pois or sheaves on a cable come too close together (<1mm) then they will be pushed away from eachother.
    This prevents the unwanted situation where multiple pois end up at the same location. In that case it can not be determined which amount of force should be applied to each of the pois.

​

Property	Read-Only	Documentation
tension	Read-only	Tension in the cable [kN]
stretch	Read-only	Stretch of the cable [m] Tension [kN] = EA [kN] * stretch [m] / length [m]
length		Length of the cable when in rest [m] Tension [kN] = EA [kN] * stretch [m] / length [m]
EA		Stiffness of the cable [kN] Tension [kN] = EA [kN] * stretch [m] / length [m]
diameter		Diameter of the cable. Used when a cable runs over a circle. [m]
connections		List or Tuple of nodes that this cable is connected to. Nodes may be passed by name (string) or by reference. Example: p1 = s.new_point(‘point 1’) p2 = s.new_point(‘point 2’, position = (0,0,10) p3 = s.new_point(‘point 3’, position = (10,0,10) c1 = s.new_circle(‘circle 1’,parent = p3, axis = (0,1,0), radius = 1) c = s.new_cable(“cable_1”, endA=”Point”, endB = “Circle”, length = 1.2, EA = 10000) c.connections = (‘point 1’, ‘point 2’, ‘point 3’) # or c.connections = (p1, p2,p3) # or c.connections = [p1, ‘point 2’, p3] # all the same Notes: 1. Circles can not be used as endpoins. If one of the endpoints is a Circle then the Point that that circle is located on is used instead. 2. Points should not be repeated directly. The following will fail: c.connections = (‘point 1’, ‘point 3’, ‘circle 1’) because the last point is a circle. So circle 1 will be replaced with the point that the circle is on: point 3. so this becomes (‘point 1’,’point 3’,’point 3’) this is invalid because point 3 is repeated.

Circle

A Circle models a circle shape based on a diameter and an axis direction

Property	Read-Only	Documentation
axis		Direction of the sheave axis (x,y,z) in parent axis system. Note: The direction of the axis is also used to determine the positive direction over the circumference of the circle. This is then used when cables run over the circle or the circle is used for geometric contacts. So if a cable runs over the circle in the wrong direction then a solution is to change the axis direction to its opposite: circle.axis =- circle.axis. (another solution in that case is to define the connections of the cable in the reverse order)
radius		Radius of the circle [m]
global_position	Read-only	Returns the global position of the center of the sheave. Note: this is the same as the global position of the parent point.
position	Read-only	Returns the local position of the center of the sheave. Note: this is the same as the local position of the parent point.

Component

Components are frame-nodes containing a scene. The imported scene is referenced by a file-name. All impored nodes are placed in the components frame.

Property	Read-Only	Documentation
name		Name of the node (str), must be unique
path		Path of the model-file. For example res: padeye.dave

Connector2d

A Connector2d linear connector with acts both on linear displacement and angular displacement.

* the linear stiffness is defined by k_linear and is defined over the actual shortest direction between nodeA and nodeB.
* the angular stiffness is defined by k_angular and is defined over the actual smallest angle between the two systems.

Property	Read-Only	Documentation
angle	Read-only	Actual angle between nodeA and nodeB [deg] (read-only)
force	Read-only	Actual force between nodeA and nodeB [kN] (read-only)
moment	Read-only	Actual moment between nodeA and nodeB [kNm] (read-only)
axis	Read-only	Actual rotation axis between nodeA and nodeB (read-only)
ax	Read-only	X component of actual rotation axis between nodeA and nodeB (read-only)
ay	Read-only	Y component of actual rotation axis between nodeA and nodeB (read-only)
az	Read-only	Z component of actual rotation axis between nodeA and nodeB (read-only)
k_linear		Linear stiffness [kN/m]
k_angular		Angular stiffness [kNm/rad]
nodeA		Connected axis system A
nodeB		Connected axis system B

ContactBall

A ContactBall is a linear elastic ball which can contact with ContactMeshes.

It is modelled as a sphere around a Poi. Radius and stiffness can be controlled using radius and k.

The force is applied on the Poi and it not registered separately.

Property	Read-Only	Documentation
can_contact	Read-only	True if the ball is currently perpendicular to at least one of the faces of one of the meshes. So when contact is possible. To check if there is contact use “force”. See Also: Force
contact_force	Read-only	Returns the force on the ball [kN, kN, kN] (global axis) The force is applied at the center of the ball See Also: contact_force_magnitude
contact_force_magnitude	Read-only	Returns the absolute force on the ball, if any [kN] The force is applied on the center of the ball See Also: contact_force
compression	Read-only	Returns the absolute compression of the ball, if any [m]
contactpoint	Read-only	The nearest point on the nearest mesh. Only defined
meshes		List of contact-mesh nodes. When getting this will yield a list of node references. When setting node references and node-names may be used. eg: ball.meshes = [mesh1, ‘mesh2’]
meshes_names	Read-only	List with the names of the meshes
radius		Radius of the contact-ball [m]
k		Compression stiffness of the ball in force per meter of compression [kN/m]

ContactMesh

A ContactMesh is a tri-mesh with an axis parent

Property	Read-Only	Documentation
trimesh	Read-only	The TriMeshSource object which can be used to change the mesh Example: s[‘Contactmesh’].trimesh.load_file(‘cube.obj’, scale = (1.0,1.0,1.0), rotation = (0.0,0.0,0.0), offset = (0.0,0.0,0.0))

CurrentArea

Abstract Based class for wind and current areas.

Property	Read-Only	Documentation
force	Read-only	The x,y and z components of the force [kN,kN,kN] (global axis)
fx	Read-only	The global x-component of the force [kN] (global axis)
fy	Read-only	The global y-component of the force [kN] (global axis)
fz	Read-only	The global z-component of the force [kN] (global axis)
A		Total area [m2]. See also Ae
Ae	Read-only	Effective area [m2]. This is the projection of the total to the actual wind/current direction. Read only.
Cd		Cd coefficient [-]
direction		Depends on ‘areakind’. For ‘plane’ this is the direction of the normal of the plane, for ‘cylindrical’ this is the direction of the axis and for ‘sphere’ this is not used [m,m,m]
areakind		Defines how to interpret the area. See also: direction

Force

A Force models a force and moment on a poi.

Both are expressed in the global axis system.

​

Property	Read-Only	Documentation
force		The x,y and z components of the force [kN,kN,kN] (global axis) Example s[‘wind’].force = (12,34,56)
fx		The global x-component of the force [kN] (global axis)
fy		The global y-component of the force [kN] (global axis)
fz		The global z-component of the force [kN] (global axis)
moment		The x,y and z components of the moment (kNm,kNm,kNm) in the global axis system. Example s[‘wind’].moment = (12,34,56)
mx		The global x-component of the moment [kNm] (global axis)
my		The global y-component of the moment [kNm] (global axis)
mz		The global z-component of the moment [kNm] (global axis)

Frame

Axis

Axes are the main building blocks of the geometry. They have a position and an rotation in space. Other nodes can be placed on them.
Axes can be nested by parent/child relationships meaning that an axis can be placed on an other axis.
The possible movements of an axis can be controlled in each degree of freedom using the "fixed" property.

Axes are also the main building block of inertia.
Dynamics are controlled using the inertia properties of an axis: inertia [mT], inertia_position[m,m,m] and inertia_radii [m,m,m]


Notes:
     - circular references are not allowed: It is not allowed to place a on b and b on a

​

Property	Read-Only	Documentation
inertia		The linear inertia of the axis in [mT] Aka: “Mass” - used only for dynamics
inertia_position		The position of the center of inertia. Aka: “cog” [m,m,m] (local axis) - used only for dynamics - defined in local axis system
inertia_radii		The radii of gyration of the inertia [m,m,m] (local axis) Used to calculate the mass moments of inertia via Ixx = rxx^2 * inertia Iyy = rxx^2 * inertia Izz = rxx^2 * inertia Note that DAVE does not directly support cross terms in the interia matrix of an axis system. If you want to use cross terms then combine multiple axis system to reach the same result. This is because inertia matrices with diagonal terms can not be translated.
fixed		Determines which of the six degrees of freedom are fixed, if any. (x,y,z,rx,ry,rz). True means that that degree of freedom will not change when solving statics. False means a that is may be changed in order to find equilibrium. These are the expressed on the coordinate system of the parent (if any) or the global axis system (if no parent) See Also: set_free, set_fixed
x		The x-component of the position vector (parent axis) [m]
y		The y-component of the position vector (parent axis) [m]
z		The z-component of the position vector (parent axis) [m]
position		Position of the axis (parent axis) [m,m,m] These are the expressed on the coordinate system of the parent (if any) or the global axis system (if no parent)
rx		The x-component of the rotation vector [degrees] (parent axis)
ry		The y-component of the rotation vector [degrees] (parent axis)
rz		The z-component of the rotation vector [degrees], (parent axis)
rotation		Rotation of the axis about its origin (rx,ry,rz). Defined as a rotation about an axis where the direction of the axis is (rx,ry,rz) and the angle of rotation is
parent		Determines the parent of the axis. Should either be another axis or ‘None’ Other axis may be refered to by reference or by name (str). So the following are identical p = s.new_frame(‘parent_axis’) c = s.new_frame(‘child axis’) c.parent = p c.parent = ‘parent_axis’ To define that an axis does not have a parent use c.parent = None
gx		The x-component of the global position vector [m] (global axis )
gy		The y-component of the global position vector [m] (global axis )
gz		The z-component of the global position vector [m] (global axis )
global_position		The global position of the origin of the axis system [m,m,m] (global axis)
grx		The x-component of the global rotation vector [degrees] (global axis)
gry		The y-component of the global rotation vector [degrees] (global axis)
grz		The z-component of the global rotation vector [degrees] (global axis)
tilt_x	Read-only	Tilt percentage. This is the z-component of the unit y vector [%]. See Also: heel
heel	Read-only	Heel in degrees. SB down is positive [deg]. This is the inverse sin of the unit y vector(This is the arcsin of the tiltx) See also: tilt_x
tilt_y	Read-only	Tilt percentage. This is the z-component of the unit -x vector [%]. So a positive rotation about the y axis results in a positive tilt_y. See Also: trim
trim	Read-only	Trim in degrees. Bow-down is positive [deg]. This is the inverse sin of the unit -x vector(This is the arcsin of the tilt_y) See also: tilt_y
heading	Read-only	Direction (0..360) [deg] of the local x-axis relative to the global x axis. Measured about the global z axis heading = atan(u_y,u_x) typically: heading 0 –> local axis align with global axis heading 90 –> local x-axis in direction of global y axis See also: heading_compass
heading_compass	Read-only	The heading (0..360)[deg] assuming that the global y-axis is North and global x-axis is East and rotation accoring compass definition
global_rotation		Rotation [deg,deg,deg] (global axis)
global_transform	Read-only	Read-only: The global transform of the axis system [matrix]
connection_force	Read-only	The forces and moments that this axis applies on its parent at the origin of this axis system. [kN, kN, kN, kNm, kNm, kNm] (Parent axis) If this axis would be connected to a point on its parent, and that point would be located at the location of the origin of this axis system then the connection force equals the force and moment applied on that point. Example: parent axis with name A this axis with name B this axis is located on A at position (10,0,0) there is a Point at the center of this axis system. A force with Fz = -10 acts on the Point. The connection_force is (-10,0,0,0,0,0) This is the force and moment as applied on A at point (10,0,0)
connection_force_x	Read-only	The x-component of the connection-force vector [kN] (Parent axis)
connection_force_y	Read-only	The y-component of the connection-force vector [kN] (Parent axis)
connection_force_z	Read-only	The z-component of the connection-force vector [kN] (Parent axis)
connection_moment_x	Read-only	The mx-component of the connection-force vector [kNm] (Parent axis)
connection_moment_y	Read-only	The my-component of the connection-force vector [kNm] (Parent axis)
connection_moment_z	Read-only	The mx-component of the connection-force vector [kNm] (Parent axis)
applied_force	Read-only	The force and moment that is applied on origin of this axis [kN, kN, kN, kNm, kNm, kNm] (Global axis)
ux	Read-only	The unit x axis [m,m,m] (Global axis)
uy	Read-only	The unit y axis [m,m,m] (Global axis)
uz	Read-only	The unit z axis [m,m,m] (Global axis)
equilibrium_error	Read-only	The remaining force and moment on this axis. Should be zero when in equilibrium (applied-force minus connection force, Parent axis)

GeometricContact

GeometricContact

A GeometricContact can be used to construct geometric connections between circular members:
    - 	steel bars and holes, such as a shackle pin in a padeye (pin-hole)
    -	steel bars and steel bars, such as a shackle-shackle connection


Situation before creation of geometric contact:

Axis1
    Point1
        Circle1
Axis2
    Point2
        Circle2

Create a geometric contact with Circle1 and parent and Circle2 as child

Axis1
    Point1              : observed, referenced as parent_circle_parent
        Circle1         : observed, referenced as parent_circle

    _axis_on_parent                 : managed
        _pin_hole_connection        : managed
            _connection_axial_rotation : managed
                _axis_on_child      : managed
                    Axis2           : managed    , referenced as child_circle_parent_parent
                        Point2      : observed   , referenced as child_circle_parent
                            Circle2 : observed   , referenced as child_circle

​

Property	Read-Only	Documentation
name		Name of the node (str), must be unique
child		The Circle that is connected to the GeometricContact [Node] See Also: parent
parent		The Circle that the GeometricConnection is connected to [Node] See Also: child
swivel		Swivel angle between parent and child objects [degrees]
swivel_fixed		Allow parent and child to swivel relative to eachother [boolean]
rotation_on_parent		Angle between the line connecting the centers of the circles and the axis system of the parent node [degrees]
fixed_to_parent		Allow rotation around parent [boolean] see also: rotation_on_parent
child_rotation		Angle between the line connecting the centers of the circles and the axis system of the child node [degrees]
child_fixed		Allow rotation of child relative to connection, see also: child_rotation [boolean]
inside		Type of connection: True means child circle is inside parent circle, False means the child circle is outside but the circumferences contact [boolean]

HydSpring

A HydSpring models a linearized hydrostatic spring.

The cob (center of buoyancy) is defined in the parent axis system.
All other properties are defined relative to the cob.

​

Property	Read-Only	Documentation
cob		Center of buoyancy in parent axis system (m,m,m)
BMT		Vertical distance between cob and metacenter for roll [m]
BML		Vertical distance between cob and metacenter for pitch [m]
COFX		Horizontal x-position Center of Floatation (center of waterplane area), relative to cob [m]
COFY		Horizontal y-position Center of Floatation (center of waterplane area), relative to cob [m]
kHeave		Heave stiffness [kN/m]
waterline		Waterline-elevation relative to cob for un-stretched heave-spring. Positive if cob is below the waterline (which is where is normally is) [m]
displacement_kN		Displacement when waterline is at waterline-elevation [kN]

LC6d

A LC6d models a Linear Connector with 6 dofs.

It connects two Axis elements with six linear springs.

The first axis system is called "main", the second is called "secondary". The difference is that
the "main" axis system is used for the definition of the stiffness values.

The translational-springs are easy. The rotational springs may not be as intuitive. They are defined as:

  - rotation_x = arc-tan ( uy[0] / uy[1] )
  - rotation_y = arc-tan ( -ux[0] / ux[2] )
  - rotation_z = arc-tan ( ux[0] / ux [1] )

which works fine for small rotations and rotations about only a single axis.

Tip:
It is better to use use the "fixed" property of axis systems to create joints.

​

Property	Read-Only	Documentation
stiffness		Stiffness of the connector: kx, ky, kz, krx, kry, krz in [kN/m and kNm/rad] (axis system of the main axis)
main		Main axis system. This axis system dictates the axis system that the stiffness is expressed in
secondary		Secondary (connected) axis system
fgx	Read-only	Force on main in global coordinate frame [kN]
fgy	Read-only	Force on main in global coordinate frame [kN]
fgz	Read-only	Force on main in global coordinate frame [kN]
force_global	Read-only	Force on main in global coordinate frame [kN]
mgx	Read-only	Moment on main in global coordinate frame [kNm]
mgy	Read-only	Moment on main in global coordinate frame [kNm]
mgz	Read-only	Moment on main in global coordinate frame [kNm]
moment_global	Read-only	Moment on main in global coordinate frame [kNm]

Point

A location on an axis

Property	Read-Only	Documentation
x		x component of local position [m] (parent axis)
y		y component of local position [m] (parent axis)
z		z component of local position [m] (parent axis)
applied_force	Read-only	Applied force [kN,kN,kN] (parent axis)
force	Read-only	total force magnitude as applied on the point [kN]
fx	Read-only	x component of applied force [kN] (parent axis)
fy	Read-only	y component of applied force [kN] (parent axis)
fz	Read-only	z component of applied force [kN] (parent axis)
applied_moment	Read-only	Applied moment [kNm,kNm,kNm] (parent axis)
moment	Read-only	total moment magnitude as applied on the point [kNm]
mx	Read-only	x component of applied moment [kNm] (parent axis)
my	Read-only	y component of applied moment [kNm] (parent axis)
mz	Read-only	z component of applied moment [kNm] (parent axis)
position		Local position [m,m,m] (parent axis)
applied_force_and_moment_global	Read-only	Applied force and moment on this point [kN, kN, kN, kNm, kNm, kNm] (Global axis)
gx		x component of position [m] (global axis)
gy		y component of position [m] (global axis)
gz		z component of position [m] (global axis)
global_position		Global position [m,m,m] (global axis)

RigidBody

A Rigid body, internally composed of an axis, a point (cog) and a force (gravity)

Property	Read-Only	Documentation
name		Name of the node (str), must be unique
footprint		Sets the footprint vertices. Supply as an iterable with each element containing three floats
cogx		x-component of cog position [m] (local axis)
cogy		y-component of cog position [m] (local axis)
cogz		z-component of cog position [m] (local axis)
cog		Center of Gravity position [m,m,m] (local axis)
mass		Static mass of the body [mT] See Also: inertia

SPMT

An SPMT is a Self-propelled modular transporter

These are platform vehicles

============  =======
0 0 0 0 0 0   0 0 0 0

A number of axles share a common suspension system.

The SPMT node models such a system of axles.

The SPMT is attached to an axis system.
The upper locations of the axles are given as an array of 3d vectors.

Rays are extended from these points in local -Z direction (down) until they hit a contact-shape.

If no contact shape is found (or not within the maximum distance per axles) then the maximum defined extension for that axle is used.

A shared pressure is obtained from the combination of all individual extensions.

Finally an equal force is applied on all the axle connection points. This force acts in local Z direction.

​

Property	Read-Only	Documentation
axle_force	Read-only	Returns the force on each of the axles [kN, kN, kN] (global axis)
compression	Read-only	Returns the total compression of all the axles together [m]
k		Compression stiffness of the ball in force per meter of compression [kN/m]
nominal_length		Average Axle extension (defined point to bottom of wheel) for zero force [m]
max_length		Maximum axle extension per axle (defined point to bottom of wheel) [m]
meshes		List of contact-mesh nodes. When getting this will yield a list of node references. When setting node references and node-names may be used. eg: ball.meshes = [mesh1, ‘mesh2’]
meshes_names	Read-only	List with the names of the meshes
axles		Axles is a list axle positions. Each entry is a (x,y,z) entry which determines the location of the axle on SPMT. This is relative to the parent of the SPMT. Example: [(-10,0,0),(-5,0,0),(0,0,0)] for three axles

Shackle

Green-Pin Heavy Duty Bow Shackle BN

visual from: https://www.traceparts.com/en/product/green-pinr-p-6036-green-pinr-heavy-duty-bow-shackle-bn-hdgphm0800-mm?CatalogPath=TRACEPARTS%3ATP04001002006&Product=10-04072013-086517&PartNumber=HDGPHM0800
details from: https://www.greenpin.com/sites/default/files/2019-04/brochure-april-2019.pdf

wll a b c d e f g h i j k weight
[t] [mm]  [kg]
120 95 95 208 95 147 400 238 647 453 428 50 110
150 105 108 238 105 169 410 275 688 496 485 50 160
200 120 130 279 120 179 513 290 838 564 530 70 235
250 130 140 299 130 205 554 305 904 614 565 70 295
300 140 150 325 140 205 618 305 996 644 585 80 368
400 170 175 376 164 231 668 325 1114 690 665 70 560
500 180 185 398 164 256 718 350 1190 720 710 70 685
600 200 205 444 189 282 718 375 1243 810 775 70 880
700 210 215 454 204 308 718 400 1263 870 820 70 980
800 210 220 464 204 308 718 400 1270 870 820 70 1100
900 220 230 485 215 328 718 420 1296 920 860 70 1280
1000 240 240 515 215 349 718 420 1336 940 900 70 1460
1250 260 270 585 230 369 768 450 1456 1025 970 70 1990
1500 280 290 625 230 369 818 450 1556 1025 1010 70 2400

Returns:

​

Property	Read-Only	Documentation
kind		Type of shackle, for example GP800 [text]
name		Name of the node (str), must be unique

Sling

A Sling is a single wire with an eye on each end. The eyes are created by splicing the end of the sling back into the itself.

The geometry of a sling is defined as follows:

diameter : diameter of the wire
LeyeA, LeyeB : inside lengths of the eyes
LsplicaA, LspliceB : the length of the splices
Ultimate length : the distance between the insides of ends of the eyes A and B when pulled straight (= Ultimate Length).

Stiffness:
The stiffness of the sling is specified by a single value: EA. EA can be set directly or by providing a k_total
This determines the stiffnesses of the individual parts as follows:
Wire in the eyes: EA
Splices: Infinity (rigid)

See Also: Grommet

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Property	Read-Only	Documentation
name		Name of the node (str), must be unique
k_total		Total stiffness of the sling in kN/m
length		Total length measured between the INSIDE of the eyes of the sling is pulled straight. [m]
LeyeA		Total length inside eye A if stretched flat [m]
LeyeB		Total length inside eye B if stretched flat [m]
LspliceA		Length of the splice at end A [m]
LspliceB		Length of the splice at end B [m]
diameter		Diameter of the sling (except the splices) [m]
EA		EA of the wire of the sling. See also: k_total
mass		Mass and weight of the sling. This mass is discretized distributed over the two splices [mT]
endA		End A [circle or point node]
endB		End B [circle or point node]
sheaves		List of sheaves (circles, points) that the sling runs over between the two ends. May be provided as list of nodes or node-names.

Tank

Tank provides a fillable tank based on a mesh. The mesh is triangulated and chopped at the instantaneous flat fluid surface. Gravity is applied as an downwards force that the center of fluid. The calculation of fluid volume and center is as accurate as the provided geometry.

There as no restrictions to the size or aspect ratio of the panels. It is excellent to model as box using 6 faces. Using smaller panels has a negative effect on performance.

The normals of the panels should point *away* from the fluid. This means that the same basic shapes can be used for both buoyancy and tanks.

Property	Read-Only	Documentation
trimesh	Read-only	The TriMeshSource object which can be used to change the mesh Example: s[‘Contactmesh’].trimesh.load_file(‘cube.obj’, scale = (1.0,1.0,1.0), rotation = (0.0,0.0,0.0), offset = (0.0,0.0,0.0))
free_flooding		Tank is filled till global waterline (aka: damaged) [bool]
permeability		Permeability is the fraction of the enclosed volume that can be filled with fluid [-]
cog	Read-only	Returns the GLOBAL position of the center of volume / gravity
cog_local	Read-only	Returns the local position of the center of gravity
cog_when_full	Read-only	Returns the LOCAL position of the center of volume / gravity of the tank when it is filled
fill_pct		Amount of volume in tank as percentage of capacity [%]
level_global		The fluid plane elevation in the global axis system. Setting this adjusts the volume
volume		The actual volume of fluid in the tank in m3. Setting this adjusts the fluid level
density		Density of the fluid in the tank in mT/m3
capacity	Read-only	Returns the capacity of the tank in m3. This is calculated from the defined geometry and permeability.
ullage	Read-only	Ullage of the tank [m]. The ullage is the distance between a measurement point and the fluid surface. The point is [xf,yf,zv] where xf and yf are the x and y coordinates (local) of the center of fluid when the tank is full. zv is the largest z value of all the vertices of the tank. The measurement direction is in local z-direction. If the tank is under an angle then this is not perpendicular to the fluid. It is possible that this definition returns an ullage larger than the physical tank depth. In that case the physical depth of the tank is returned instead.

Visual

Visual

.. image:: ./images/visual.png

A Visual node contains a 3d visual, typically obtained from a .obj file.
A visual node can be placed on an axis-type node.

It is used for visualization. It does not affect the forces, dynamics or statics.

The visual can be given an offset, rotation and scale. These are applied in the following order

1. rotate
2. scale
3. offset

Hint: To scale before rotation place the visual on a dedicated axis and rotate that axis.

​

Property	Read-Only	Documentation
file_path	Read-only	Resolved path of the visual (str)

WaveInteraction1

WaveInteraction

Wave-interaction-1 couples a first-order hydrodynamic database to an axis.

This adds:
- wave-forces
- damping
- added mass

The data is provided by a Hyddb1 object which is defined in the MaFreDo package. The contents are not embedded
but are to be provided separately in a file. This node contains only the file-name.

​

Property	Read-Only	Documentation
file_path	Read-only	Resolved path of the visual (str)

WindArea

Abstract Based class for wind and current areas.

Property	Read-Only	Documentation
force	Read-only	The x,y and z components of the force [kN,kN,kN] (global axis)
fx	Read-only	The global x-component of the force [kN] (global axis)
fy	Read-only	The global y-component of the force [kN] (global axis)
fz	Read-only	The global z-component of the force [kN] (global axis)
A		Total area [m2]. See also Ae
Ae	Read-only	Effective area [m2]. This is the projection of the total to the actual wind/current direction. Read only.
Cd		Cd coefficient [-]
direction		Depends on ‘areakind’. For ‘plane’ this is the direction of the normal of the plane, for ‘cylindrical’ this is the direction of the axis and for ‘sphere’ this is not used [m,m,m]
areakind		Defines how to interpret the area. See also: direction