Experimental Investigation of the hydrodynamic and acoustic performance of a Gate Rudder® system over a conventional rudder

The Gate Rudder® is a new concept of energy saving device and manoeuvring system, consisting of two asymmetric and independent blades at each side of a propeller which combines the advantage to deliver additional thrust, similar to an accelerating ducted propulsor, and to enhance ship manoeuvrability and seakeeping ability due to the individual control of each rudder blades. The present study reports the results of a comprehensive experimental survey in which the hydrodynamic and hydro-acoustic performances of a Gate Rudder® system (GRS) were investigated with respect to a conventional rudder (CRS), for a reference container vessel. The survey, that was conducted in the framework of the EU H2020 Research Project “GATERS”, included detailed flow measurements by 2D-PIV and Stereo-PIV, cavitation tests and acoustic measurements on a scaled model of a target container ship. The tests matrix covered different rudder/rudder-blade angles, speeds and displacements. The study highlights the beneficial effects provided by the installation of a Gate Rudder® over a conventional rudder in terms of sound mitigation and reveals the fundamental underlying hydrodynamic mechanisms of the propeller wake interaction with the Gate Rudder blades under different operative conditions. The results provide useful insights on how to improve the hydrodynamic and acoustic performance of a GRS.