# 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

Documentation

target_elevation

The target elevation of the parent of the ballast system.

cogx

X position of combined CoG of all tank contents in the ballast-system. (global coordinate) [m]

cogy

Y position of combined CoG of all tank contents in the ballast-system. (global coordinate) [m]

cogz

Z position of combined CoG of all tank contents in the ballast-system. (global coordinate) [m]

cog

Combined CoG of all tank contents in the ballast-system. (global coordinate) [m,m,m]

weight

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

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

Moment on beam at node A (kNm, kNm, kNm) , axis system of node A

moment_B

Moment on beam at node B (kNm, kNm, kNm) , axis system of node B

tension

Tension in the beam [kN], negative for compression

tension is calculated at the midpoints of the beam segments.

torsion

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

Returns the x-positions of the end nodes and internal nodes along the length of the beam [m]

X_midpoints

X-positions of the beam centers measured along the length of the beam [m]

global_positions

Global-positions of the end nodes and internal nodes [m,m,m]

global_orientations

Global-orientations of the end nodes and internal nodes [deg,deg,deg]

bending

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

Documentation

trimesh

Reference to TriMeshSource object

cob

GLOBAL position of the center of buoyancy [m,m,m] (global axis)

cob_local

Position of the center of buoyancy [m,m,m] (local axis)

displacement

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

Documentation

tension

Tension in the cable [kN]

stretch

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

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)

global_position

Returns the global position of the center of the sheave.

Note: this is the same as the global position of the parent point.

position

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

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

Documentation

angle

Actual angle between nodeA and nodeB [deg] (read-only)

force

Actual force between nodeA and nodeB [kN] (read-only)

moment

Actual moment between nodeA and nodeB [kNm] (read-only)

axis

Actual rotation axis between nodeA and nodeB (read-only)

ax

X component of actual rotation axis between nodeA and nodeB (read-only)

ay

Y component of actual rotation axis between nodeA and nodeB (read-only)

az

Z component of actual rotation axis between nodeA and nodeB (read-only)

k_linear

Linear stiffness [kN/m]

k_angular

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

Documentation

can_contact

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”.

contact_force

Returns the force on the ball [kN, kN, kN] (global axis)

The force is applied at the center of the ball

contact_force_magnitude

Returns the absolute force on the ball, if any [kN]

The force is applied on the center of the ball

compression

Returns the absolute compression of the ball, if any [m]

contactpoint

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

List with the names of the meshes

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

Documentation

trimesh

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

Documentation

force

The x,y and z components of the force [kN,kN,kN] (global axis)

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)

A

Ae

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

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

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

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)

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

Tilt percentage. This is the z-component of the unit y vector [%].

heel

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)

tilt_y

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.

trim

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)

Direction (0..360) [deg] of the local x-axis relative to the global x axis. Measured about the global z axis

typically:
heading 0 –> local axis align with global axis
heading 90 –> local x-axis in direction of global y axis

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: The global transform of the axis system [matrix]

connection_force

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

The x-component of the connection-force vector [kN] (Parent axis)

connection_force_y

The y-component of the connection-force vector [kN] (Parent axis)

connection_force_z

The z-component of the connection-force vector [kN] (Parent axis)

connection_moment_x

The mx-component of the connection-force vector [kNm] (Parent axis)

connection_moment_y

The my-component of the connection-force vector [kNm] (Parent axis)

connection_moment_z

The mx-component of the connection-force vector [kNm] (Parent axis)

applied_force

The force and moment that is applied on origin of this axis [kN, kN, kN, kNm, kNm, kNm] (Global axis)

ux

The unit x axis [m,m,m] (Global axis)

uy

The unit y axis [m,m,m] (Global axis)

uz

The unit z axis [m,m,m] (Global axis)

equilibrium_error

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

Documentation

name

Name of the node (str), must be unique

child

The Circle that is connected to the GeometricContact [Node]

parent

The Circle that the GeometricConnection is connected to [Node]

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]

child_rotation

Angle between the line connecting the centers of the circles and the axis system of the child node [degrees]

child_fixed

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

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

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

Force on main in global coordinate frame [kN]

fgy

Force on main in global coordinate frame [kN]

fgz

Force on main in global coordinate frame [kN]

force_global

Force on main in global coordinate frame [kN]

mgx

Moment on main in global coordinate frame [kNm]

mgy

Moment on main in global coordinate frame [kNm]

mgz

Moment on main in global coordinate frame [kNm]

moment_global

Moment on main in global coordinate frame [kNm]

## Point¶

A location on an axis

Property

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

Applied force [kN,kN,kN] (parent axis)

force

total force magnitude as applied on the point [kN]

fx

x component of applied force [kN] (parent axis)

fy

y component of applied force [kN] (parent axis)

fz

z component of applied force [kN] (parent axis)

applied_moment

Applied moment [kNm,kNm,kNm] (parent axis)

moment

total moment magnitude as applied on the point [kNm]

mx

x component of applied moment [kNm] (parent axis)

my

y component of applied moment [kNm] (parent axis)

mz

z component of applied moment [kNm] (parent axis)

position

Local position [m,m,m] (parent axis)

applied_force_and_moment_global

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

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]

## 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

Documentation

axle_force

Returns the force on each of the axles [kN, kN, kN] (global axis)

compression

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

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

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)



Property

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

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

Documentation

trimesh

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

Returns the GLOBAL position of the center of volume / gravity

cog_local

Returns the local position of the center of gravity

cog_when_full

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

Returns the capacity of the tank in m3. This is calculated from the defined geometry and permeability.

ullage

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

## TriMeshSource¶

TriMesh

A TriMesh node contains triangular mesh which can be used for buoyancy or contact


Property

Documentation

## 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

Documentation

file_path

Resolved path of the visual (str)

## WaveInteraction1¶

WaveInteraction

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

- wave-forces
- damping

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

Documentation

file_path

Resolved path of the visual (str)

## WindArea¶

Abstract Based class for wind and current areas.

Property

Documentation

force

The x,y and z components of the force [kN,kN,kN] (global axis)

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)

A

Ae

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