Investigation about hydrodynamic characteristics of a collaborative spoiled rudder considering the effect of the propeller

The hydrodynamic performance of a novel collaborative spoiled rudder (CSR) operating in the wake of a propeller is investigated comprehensively through numerical simulations. The CSR is designed for improving the navigation performance by employing two independently controllable spoilers. The complex interaction between a B4-55 propeller and a conventional rudder (CR) modified into the CSR is analyzed systematically. This research encompasses global force analysis, unsteady flow characterization, and strategic operational optimization. Key findings reveal that the opened spoiler significantly enhances the rudder's effectiveness. The spoilers' presence also modestly affects the upstream propeller, leading to a slight reduction in thrust and an increase in torque. A pivotal contribution is the development and application of an equal lift analysis strategy, which demonstrates that for high-maneuvering scenarios requiring large lift, the CSR can achieve performance equivalent to the CR operating at a larger deflection angle, but with a smaller rudder deflection angle and an optimal spoiler open angle, thereby potentially improving efficiency. Spectral analysis of unsteady forces indicates that the CSR effectively suppresses low-frequency, high-amplitude load fluctuations, promoting a more favorable load spectrum. Furthermore, the CSR exhibits superior performance in course-keeping mode. With the rudder blade fixed at zero deflection, precise lateral forces can be generated through spoiler-only control, achieving higher efficiency and drastically lower actuation torque compared to using a slightly deflected CR. This work concludes that the CSR offers a balanced and optimized approach to ship maneuverability, course-keeping efficiency, and control energy savings.