Steady course through the waves
Powered by wind, it is important that the vessels of the Oceanbird concept will perform well at the windy sea. Watch when a five-metre model were exposed to difficult waves in the basin at SSPA.
Developing the Oceanbird concept, involves a large amount of computer simulations of the ship’s performance and behaviour. As one of our partners in the development project, SSPA are performing extensive model tests. A five-metre long model have now been tested in SSPA´s large basin, the Maritime Dynamics Laboratory in Gothenburg, Sweden.
The purpose of the model tests is to generate data for checking and tuning the computer simulations. The motions and accelerations when the ship sails through the waves is an important input to the structural design of the wing sails. A second purpose of the tests is to discover unexpected behaviour that the computer simulations may fail to predict.
The ship model could be run in three modes: conventional engine mode using under-water propellers, sailing mode and combined sailing and engine mode. The characteristic Oceanbird wing sails were in the model tests replaced by two air fans on top of the deck. The fans generated the same forces as the wing sails will do.
The team wanted to see the model sail without assistance from propellers. Especially in more difficult conditions, for example larger waves, following waves and head seas.
“The toughest test we will do is with stern waves corresponding to six-metre in full scale coming from behind” says Sofia Werner, Manager Strategic Research Hydrodynamics at SSPA.
Could Oceanbird keep a steady course?
When you drive the ship in sailing mode instead of conventional engine mode, the driving force is acting above deck and more forward. This changes the way the ship responds to the rudder actions when the auto pilot tries to keep the ship on the given course.
“In general, we are really surprised at how well she sails. She keeps the course even in moderate waves. We have both gathered this important validation data but also gained a better understanding of how the vessel will behave in the real world.
It’s fantastic to see that the vessel can actually sail without any other assistance than the wind. We will be able to sail this ship in the North Atlantic Ocean with six-metre waves, and she will perform well” says Sofia Werner.