Ships that equipped with flapped rudders have better manoeuvring performance than ships fitted with traditional spade rudders. Moreover, this advantage is achieved without significantly affecting the ship's resistance during normal cruising. Flapped rudders are, therefore, favourable for ships that require high manoeuvring performance and sail long distance. Nowadays, there is a trend of using twin flapped rudders on newly built inland vessels in the Yangtze River. To properly design these ships and analyse their manoeuvring performance, the hydrodynamic characteristics of the flapped rudders are required. In this paper, a RANS study is performed to analyse the impacts of the three main properties of a flapped rudder on its hydrodynamic coefficients. The target properties are the rudder profile, the flaplinkage ratio (the flapped angle relative to the rudder chord line divided by the applied rudder angle), and the flap-area ratio (the sectional area of the flap divided by the total sectional area). The RANS simulations are carried out with commercial meshing tool ANSYS Meshing and CFD solver ANSYS Fluent.

Ship manoeuvrability is important for navigation safety. However, few studies have been specifically carried out for inland vessels. Since most of the empirical methods were generated based on databases of seagoing ships, the usability of these methods for inland vessels is doubtful. The objective of the present work is to assess the existing manoeuvrability models and find the most suitable ones for inland vessels. Furthermore, these models are integrated into a single new model that can predict the manoeuvring behaviour of benchmark inland vessels without extensive experimental tests. The method aims at inland ships of typical dimensions in the Yangtze River (inland ships on European waterways have different dimensions), which is characterised by a large water depth. After preselecting the most promising methods through reviewing literature, a selection of the empirical methods for hull forces and moments is performed by comparing simulation results to model-scale free-running experiments of various turning and zigzag manoeuvres. Considering the large variety of rudder configurations for inland vessels, this paper describes a procedure of using 2D open-water RANS results to calculate the rudder forces and moments. Accordingly, hydrodynamic coefficients of benchmark rudder profiles are provided to apply the proposed procedure for different rudder configurations.