Evaluating the effects of drift angle on the self-propelled ship using Blade Element Momentum Theory

Ship maneuverability is one of the most essential performance indicators in the ship design process. Common practice for predicting a ship’s maneuvering characteristics and force derivatives includes theoretical methods, towing tank tests and numerical approaches via Computational Fluid Dynamics (CFD). Theoretical methods are mainly applicable to slender bodies and the interactions between the hull, the propeller and the rudder are usually not considered. In a towing tank test, forces and moments on the model ship can be measured in static and dynamic Planar Motion Mechanism (PMM) tests or Circular Motion Test (CMT) (Islam and Soares, 2018). However, conducting maneuvering tests in a towing tank or wave basin requires more accurate test facilities and ship models, which are very costly. Although traditional experimental tests in a conventional towing tank plays a significant role in evaluating ship’s maneuvering performance, with rapid development in high performance computers and numerical techniques, CFD tools provides researchers with a more efficient and economic method to compute ship maneuvering characteristics on more complex and realistic ship geometries. Carrica et al.(2013) conducted model and full-scale CFD computations of a surface combatant undergoing turning circle and zig-zag maneuvers using a simplified body force propeller model and adopted an overset grid approach to capture the ship motions and rudder movement. The URANS code CFDShip-Iowa was used for simulations and results agreed well with experimental data. Sigmund and el Moctar (2017) applied a sliding mesh approach to compute the complex hull-propeller-rudder interaction and predicted free running ship behavior in waves. This demonstrates the capability of numerical method in simulating ship maneuvering performance. More recently, Sanada et al. (2021) investigated the hull-propeller-rudder interactions of the KRISO Container Ship (KCS) with the aim of providing a physical explanation for the differences between the port and starboard turning circles using a combined experimental and CFD method. Although numerical methods can, in principle, provide an adequate description of all physics, this kind of analysis is still considered as state-of-art research ratherhan engineering practice (Zhang et al., 2017). On the one hand, large computational resources and long CPU time are required in numerical approaches. On the other hand, according to Skejic (2013), many technical difficulties concerning the analysis of ship maneuvering in realistic seaway are still not solved, such as the accuracy of the selected turbulence model, the adequacy of the propeller and rudder models under large angles of attack, the appearance of the crossflow shed vortices and more. Therefore, this paper aims to study the self-propelled KCS at a series of fixed drift angles, which represent different stages of a maneuver. This is done instead of studying the complete time varying maneuver. This kind of modelling not only significantly reduces the computational cost but also helps to guide future experimental measurements of rudder and propeller forces. Detailed results and discussion on the influence of a series of drift angles on resistance, wake velocity contours, side force and yaw moment will be presented. All simulations are conducted in calm water condition using the open source RANS solver simpleFoam which is part of OpenFOAM v7