Table of Contents

Tower Outputs

Tower outputs such as loads and kinematics may be reported at the mesh nodes for the tower.

Tower kinematics

The translation and rotational deflections of mesh nodes are reported in the tower body-fixed frame. In addition the translation and angular velocities and accelerations are also reported at the mesh nodes in the tower body-fixed frame.

Tower loads

Tower loads can be output at each mesh node. The loads are reported in the deflected mesh node frame. The direction of the axes for the tower internal loads are described below and in Figure 1.

  • XT: Aligned with the mesh node frame \(x_m\) axis. When the tower is not deflected it matches the body-fixed \(x_b\) axis. Moves with tower deflection.
  • ZT: Follows the deflected tower axis (mesh node frame \(z_m\)).
  • YT: Aligned with the mesh node frame \(y_m\) axis. When the tower is not deflected it matches the body-fixed \(y_b\) axis. Moves with tower deflection.

Origin at the mesh node where tower Cans adjoin.

Coordinate system for tower loads and deflections

Figure 1: Co-ordinate system for tower load output

The logged series are:

  • Tower Fx - Force along the local \(x_m\)-axis.
  • Tower Fy - Force along the local \(y_m\)-axis.
  • Tower Fxy - The resultant force of \(F_x\) and \(F_y\).
  • Tower Fz - The force along the local \(z_m\)-axis.
  • Tower Mx - Bending moment about the local \(x_m\)-axis.
  • Tower My - Bending moment about the local \(y_m\)-axis.
  • Tower Mxy - The resulting bending moment of $M_x$and \(M_y\).
  • Tower Mz - Bending moment about the local \(z_m\)-axis.
Note

The loads are reported based on an element-node pair basis. This means the loads at a mesh node must be given with respect to one of the elements that adjoins the node. For monopile towers this will create some ambiguity regarding the "side" of the node that is used for outputting loads for intermediate mesh nodes. For these intermediate mesh nodes the loads are reported from the lower element that adjoins the mesh node. The tower base and tower top mesh node load outputs are unambiguous as only one element connects to the aforementioned nodes. The loads are reported with respect to the upper element at the tower base and the lower element at the tower top.