Vessel data: Time history

Time history data allow you to define the vessel motion as a series of time-dependent positions. To do so, you set the primary motion or superimposed motion calculation data (or, exceptionally, both) to time history, and then define the time history data on the primary motion or superimposed motion page (or both). These data define the vessel motion by specifying the six degrees of freedom of the vessel as a function of time.

For details of how rotations are applied, see order of application of rotations.

Because the superimposed time history motion defines the position of the datum point, measured in the primary motion frame, your time history data for the surge, sway, and heave motion must be inclusive of the offset of the datum point from the vessel's local origin. That is, if your time history data are defined as the displacement of the datum point away from its initial position you need to add in the offset, of the datum point from the vessel's local origin, into your time history data.

Notes: The time values in a vessel time history need not be equally spaced.
If there is any wave-generated motion present in a vessel's time history motion then the OrcaFlex wave data must match the wave that generated that motion. If you have suitable data for the wave elevation then you can use that to specify the wave by time history.
The position and velocity specified by a time history for the start of the simulation will not, in general, match the static state from which OrcaFlex starts the simulation. To handle this OrcaFlex uses ramping during the build-up period to smooth the transition from the static state to the position and motion given in the time history.
Primary time history is always measured relative to global axes, and superimposed time history relative to primary axes. The vessel type conventions do not have any effect on time history data.