A study conducted by Norbert Bulten, Product Performance Manager at Wärtsilä, highlighted the importance of considering different operating conditions beyond straight-sailing and calm waters. The research, part of the EU-funded CHEK project, used full-scale CFD simulations to analyze the impact of rudder steering and vessel motion. Specifically, the study compared the performance of a gate rudder concept to a conventional semi-spade rudder on a Kamsarmax bulker.
The concept of a gate rudder involves two symmetrical rudder parts positioned on either side of the propeller to reduce fuel consumption and improve maneuverability. By targeting a stagnation point of the flow close to the rudder leading edge, a net-thrust force is created, enhancing the vessel’s steering capabilities. This innovative design replaces the drag of traditional rudders with a thrust-enhanced system that also reduces noise and vibration while enabling faster course changes.
The study’s findings indicated that rudders behave differently based on vessel motion, steering, and turning. Propeller loading was influenced by drift and turning, as vessel motion pre-rotates the flow to the propeller, affecting its performance at constant RPM. These insights are crucial for meeting Carbon Intensity Index (CII) regulations, signaling a shift in vessel design focus from sea-trial performance to operational efficiency. Bulten emphasized the need to reconsider traditional design approaches in response to these new operational considerations.
