Numerical seakeeping analysis determines the motions and accelerations of the ship subjected to waves, wind and current. These factors impact directly on the design of the vessel. Ship motions may hinder the vessel’s ability to complete its mission and are therefore taken into consideration when determining the principal dimensions of the ship and in developing the lines and general arrangement.

AQWA is a 3D diffraction multibody panel code. With our AQWA software from ANSYS, we can analyse the relationship between the environmental conditions and the ship’s movements and predict the ship’s response. It is then possible to optimise the design for a specific purpose and to comply with specific performance criteria.

With a numerical seakeeping analysis in frequency and time domain, it is possible to determine under which conditions the vessel is able to perform a given operation. The software tool can also be used to calculate lifting operations, mooring analysis, hook load forces and dynamic factors in cranes.

Numerous seafastening designs for wind turbine generator sets, lifting operations, ship helicopter operational limits (SHOL) and ship/ship interaction have been investigated by OSK-ShipTech A/S using AQWA.

Transport of wind turbines

When transporting wings for wind turbines, a wing immersion analysis is included in the seakeeping calculations. Wing immersion may occur if the wings extend over the barge’s side. If the wing tip hits the surface, it is likely to be damaged due to the load from the sea combined with the accelerations of the barge. Needless to say, the design must rule out the risk of wing immersion during transport. The analysis of wing immersion is carried out by monitoring the motion at a fixed point on the wing tip relative to the water surface and calculating the wave height at which the wing tip will be immersed. When a seakeeping analysis is conducted for wind turbine transportation, a wing tip immersion analysis is often assessed to find the necessary height of the supporting structure in order to avoid wing dip.