Guest
Refining the propeller design is the ongoing job of research and design engineers at Rolls-Royce. Alongside the propeller design itself, the Promas system – where propeller and rudder are integrated into a single unit to optimise hydrodynamic efficiency – has been implemented in the design. Rolls-Royce engineers started by gathering CFD information of the water flow towards the propeller. Then the design process began with Rolls-Royce proprietary software: different iterations of propeller and rudder design were tried before arriving at the optimal solution, which was then tested in physical experiments. By creating a 1:11 scale model of the Promas rudder and propeller in the test tank facilities of the Rolls-Royce Hydrodynamic Research Centre (HRC) in Kristinehamn, Sweden, the propeller design was fine-tuned not only to ensure the speed and efficiency requirements are met, but also that any potential problems with cavitation can be eliminated. Cavitation is essentially where air bubbles form in the flow of water around and behind the propeller. It is particularly challenging at high speed, and as well as affecting performance it can also have severe impacts on noise and vibration – a critical consideration for any superyacht project, especially for one close to 30 knots! Cavitation issues were identified and eliminated by adjusting the rudder design. Finally, the tests proved that the propeller performed above expectations. Project Cosmos will feature variable pitch propellers that will enable the yacht to handle both impressive cruising speeds in excess of 20 knots, as well as reaching a maximum speed close to 30 knots – a considerable achievement for an 80-metre superyacht.
