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Reducing resistance In its efforts to make hull forms and propellers more efficient, the company is also looking at air lubrication to reduce resistance, thereby increasing efficiency and leading to fuel savings, and again, it has carried out tests at MARIN. “We are now working on the system itself, aiming to further limit the losses and improve the efficiency of each system.” Currently, air lubrication systems are implemented on four vessels.


Zero emissions STX is also designing new concepts such as the recently revealed Silenseas, a carbon-free sailing cruise ship design. The Silenseas initiative highlights another major challenge – the quest for zero emission shipping. Loic thinks that full LNG cruise liners are getting very close. “I think they will be there in the next three to four years.” But zero emissions is still the ultimate target, he stresses. STX has a dedicated team working on minimising the losses of every system. This team has already helped to reduce emissions by 20%, he points out.


Automation Looking to future hydrodynamic research, a new technology of STX is the automated development of hull forms. However, Loic is not convinced that automation will completely take over the traditional development method based on skills and experience just yet. “It is supplanting traditional methods to some extent; we do a parameter study of a bulbous bow curvature and take the best one for example. We use strategic points and move them around and deploy an optimiser program. Here OPENFOAM is deployed for the solvers, RHINO for the CAD model and DAKOTA for the optimisers.


Model in bow quartering waves


Hull with three propellers and Azipods®, and pressure pulse sensors


These three tools are used in a loop and the best hull form is identified a few weeks later.


“But automation doesn’t necessarily simplify our life. We already start with quite an optimised hull form. And any improvement is dependent on which parameters you choose on the hull form. There are infinite possibilities! The question is how do you parameterise the hull form? I don’t think we will ever press a button and get the perfect hull!”


Cavitation observations


Automation is already evident when it comes to propellers and here STX is for the first time designing and manufacturing its first propeller for the next twin-screw cruise ship. “In the past other companies designed our propellers. But we have a good database and experience. MARIN is helping us optimise the propeller by using the PROCAL program.”


8 report


Interactions between hull and propeller With STX/MARIN having had a relationship for generations, the organisations have seen quite some research challenges. What are the next frontiers for research in Loic’s opinion? “One of the key research areas has got to be to optimise the performance interactions between the propeller and hull form. Ultimately, it has to be the sum of the optimum of the propeller and the hull form, rather than optimising separately. But I think it will be far in the future before we have this answer.


“We need to continue to focus on reducing the power of the ship, whilst maintaining the speed and achieving zero emissions. And of course, we must improve sailing technology by perhaps using the wind as the main propulsive power. There is an enormous amount of wind power available and it is free! Why not use this?”


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