OrcaFlex examples

Payload handling

Below is a list of links to OrcaFlex example topics. Within each topic are a number of examples which each comprise one or more simulation files, a description pdf file, workspace files and sometimes other supporting files. The files for each example are zipped for easy download. The simulation files can be opened and viewed with the demonstration version of OrcaFlex.

Payload handling

F01 Lowering hydrodynamics

In these three examples, we consider a number of effects that often need to be taken into account when doing a lifting or lowering analysis through the sea surface, and show how to model them in OrcaFlex.

The examples illustrate:

  • The effect of object size on the modelling method selected
  • Using multiple connected objects to model a complex structure
  • Modeling slam loads
  • Modelling trapped water

F02 Passive compensation

During the lowering process the heave of the vessel can result in severe motions of the payload and/or high loads on the crane.

To reduce these effects, heave compensation devices are often used. These can be active systems that adjust winch payout to keep the payload at a constant depth or passive systems where the payload is allowed to move but there is additional compliance with damping to reduce the loads on the crane when it heaves upwards.

This example considers the passive system, uusing a generic passive heave compensation (PHC) device as an example.

F03 PID controlled active winch

This package-lowering example uses a winch to model an active heave compensation device.

An external function written in Python is used to provide a feedback loop which controls the winch in response to the package's position, holding it at a constant depth.

F04 Payload transfer

This example shows a large payload being transferred from the deck of one vessel to the deck of another. Constraint objects are used to model the movements of the crane. The response of both vessels is fully calculated and therefore captures the effect of the shifting payload.

F06 Spool piece manoeuvring

This example demonstrates how to use the pre-bend facility in OrcaFlex to model a spool piece. Constant and variable slamming data is also applied to both the spool piece (modelled with a line object) and the spreader bar (modelled with a 6D buoy). Line feeding is utilized to lower the spool into the water.

F07 Suction anchor lowering

In this example we show how to model a suction anchor lowering operation.

Lowering of a suction anchor vertically through the sea surface requires careful consideration of how to account for the change in axial added mass and inertial loads as the suction anchor cap hits the sea surface, trapping a volume of water inside.