Rudders located in the stream accelerated by the propeller are prone to ventilation, which can undermine the turning ability of the vessel due to the loss of the rudder lift force. Such multiphase flow is a complex phenomenon, which is hard to numerically predict and control. The aim of this study is twofold. Firstly, the RANS-FVM is validated by simulating flow around the rudder with a high angle of attack and comparing the results with the experiments. Secondly, the rudder with fences is numerically analyzed under the same conditions in order to try to suppress the ventilation, which was found to be a successful technique.
The maneuverability of the vessel in offshore operations and complex waterways is of very high importance. Nowadays a more detailed design is required for the rudder in terms of maneuverability, environmental loads, etc. New design approaches were recently developed. You et al. (2018) developed the concept of a safe operating capability chart for a rudder area design. Based on the design, the effect of the rudder area on capability charts that are plotted according to the various environmental conditions to which the rudder is exposed is reviewed for use. Sun et al. (2018) made a numerical model and full-scale performance prediction for the case of the Kriso Container Ship (KCS) in which the fluctuating pressure and rudder force characteristics of a full-scale hull-propeller-rudder system were analyzed using a structured/unstructured hybrid grid combined with the Reynolds-Averaged Navier-Stokes (RANS) and Volume of Fluid (VOF) method. Shin et al. (2018) conducted research on the Wavy Twisted Rudder to increase the stalling angle compared to the Twisted Rudder. The results showed that the Wavy Twisted Rudder differed from the Twisted Rudder in terms of its delayed stall angle and high lift-drag ratio.
Furthermore, rudders which are located aft of the propeller, i.e. in the stream accelerated by the propeller, are prone to ventilation. Uncontrolled or unexpected formation of ventilation about the rotated rudder can undermine the turning ability of the vessel in a complex maneuver, due to the loss of the lift force and therefore the turning torque. Ventilation is a multiphase flow characterized by the suction of gas or a mixture of gases, most commonly the air from the free surface, within the fluid flowing around the fully or partially immersed hydrofoil. Such multiphase flow is a complex phenomenon and therefore requires both experimental and numerical analyses to explain the inception and development of the ventilation phenomenon.
