Added Inertias

Added inertias can be used to change the kinematic behaviour of a tower by adding additional mass or inertia at a specified position. These can include attachments like flanges at the connection of two tower cans as well as peripherals mounted to the structure.

At this point an added inertia can only be specified as a point-inertia.

Common properties

There are several properties, that are common to all (future) definitions. These are:

IgnoreGravityLoads: This boolean input defines if the added inertia attracts gravity or not.

HeightUpTower: This values defines the height for the attachment point of the inertia. It is measured in \(\bunit{m}\) and defined from the tower base.

SnapToNearestNode: This boolean input checks for the nearest node of the specified height. If it is true the inertia will be added to the nearest structural node, indifferent of the actual distance. Else, it is distributed (according to actual distances) among the top and bottom sections of the tower can the inertia is applied to.

Properties of Point-Inertias

Some properties are exclusive to point-inertias.

Mass: The actual mass of the attachment given at the specified height. It is measured in \(\bunit{kg}\).

Offset: This 3D-vector defines the offset relative to the already specified height point. This allows for the mass to be positioned at the outside of a tower-can. It is an optional parameter and defaults to \(\begin{bmatrix}0&0&0\end{bmatrix}^T\) if not specified. All entries are measured in \(\bunit{m}\).

MomentOfInertiaTensor: Instead of providing a mass and an offset, it is allowed to specify the moment of inertia tensor itself. Its entries are measured in \(\bunit{kgm}\).

Input of 3x3 moment of inertia tensor matrix is currently not supported.

An example of an added inertia can be found here:

{
    "Mass": 2000.0,
    "AddedInertiaType": "PointInertia",
    "IgnoreGravityLoads": false,
    "HeightUpTower": 85.00, 
    "SnapToNearestNode": false, 
    "Offset":{
        "X": 0, 
        "Y": 2,
        "Z": 0
    }
},

This represents a mass of two metric tonnes at a height of 85 meters up the tower. This mass is also located two meters to the side of the centre.

Properties of 6x6 Inertias

Input of 6x6 inertia matrix is currently not supported.