Oceanbird model tested in waves at SSPA
Recently, the research project wPCC (wind Powered Car Carrier) tested the concept Oceanbird with focus on the ship’s ability to manoeuvre and sail in waves. SSPA’s experts performed extensive model tests with a five-metre long ship model in the Maritime Dynamics Laboratory (MDL). Powered by wind, it is important that the vessel will perform well at the windy sea. The team wanted to verify that the model sails well without assistance from propellers, especially in more difficult conditions, for example larger waves, following waves and head seas. Since this was the first time a ship of this kind was tested in the basin, our experts had to develop the test techniques as well.
In September the concept Oceanbird was introduced and received worldwide attention. Wallenius Marine owns Oceanbird and SSPA and the Royal Institute of Technology (KTH) are research partners. The research- and testing programme continues by the team.
To design a concept vessel like Oceanbird a large amount of computer simulations of the ship’s performance and behaviour is needed. 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 used in these tests 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 replaced by two air fans on top of the deck. The fans generated the same forces as the wing sails will do. The wing sails were replaced by pulling air propellers, as shown in the picture below.
SSPA has tested the ship’s capability to keep a steady course, as well as the ability to rapidly change the direction. The tests started in calm water, continued to normal wave conditions, and finished with waves corresponding to six meters in full scale, i.e. very rough weather condition. The test shows that the ship sails really well even in large waves. She keeps the course without too much rudder action. In some of the toughest conditions we found that it is efficient to combine sailing and engine power, but in most conditions the ship sails perfectly well using wind only. This gives the design team support in the continuation of the design work. We are confident that the ship will sail well and cope with large waves.
Wind powered vessels of this kind has never been tested before in the MDL basin and the experts had to develop new test techniques, test methodology and test equipment. One challenge was, for example, to control the fans so that they at all time give the correct sail force when the ship model changes its speed and direction. A team of engineers and technicians from SSPA worked for months to design and build the test set-up.
- “Once the model was launched in the basin, we were all thrilled to see if it would work out. After some trimming, re-arrangement and problem solving, as usual in experimental development, all involved personnel were excited to see that the “sails” and all equipment could deliver the results we needed”, Sofia Werner, Manager Strategic Research Hydrodynamics at SSPA.
Read more about the tests with Oceanbird at www.walleniusmarine.com
Watch when a five-metre model of Oceanbird were exposed to high waves in the basin at SSPA.