CFD-based hydrodynamic analyses of ship manoeuvrability, course keeping control, and seakeeping

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Awarding institution
  • University of Strathclyde
Date of award
  • 2022
Thesis identifier
  • T16346
Person Identifier (Local)
  • 202080906
Qualification Level
Qualification Name
Department, School or Faculty
  • Ship manoeuvrability is closely related to the safety of ship operation in a real seaway; therefore, predicting a ship’s manoeuvring performance is of great importance. However, an accurate prediction of ship manoeuvrability in a real seaway is one of the most challenging problems in ship hydrodynamics, attributed to the complexity of the flow arising from the hydrodynamic interactions between the hull, propeller, rudder, and external disturbances during manoeuvres. To date, theoretical methods have been widely used for the prediction of ship manoeuvring behaviours in real sea states. These approaches rely on assumptions from the potential flow theory. However, the reliability of the potential flow theory is limited due to the lack of physics associated with viscous and turbulent effects and the free surface resolution, which are significant for manoeuvring problems. Hence, such effects which are ignored in the potential flow theory should be incorporated in the numerical codes. In light of this, Reynolds-Averaged Navier-Stokes (RANS) approaches are very attractive alternatives to the theoretical methods since they are capable of directly accounting for viscous effects in their calculations. Free-running Computational Fluid Dynamics (CFD) simulations are progressively gaining popularity for manoeuvring prediction since they are capable of incorporating viscous and turbulent effects being important on ship manoeuvring as well as do not use any consumables (as opposed to experiments). However, due to its brevity, there are no definite guidelines and recommendations regarding the numerical setup of the free-running CFD simulation in different environmental conditions such as waves, shallow waters, and currents. Given this, in this thesis, the general framework is proposed for the analysis of ship manoeuvrability, course-keeping control, and seakeeping using the unsteady RANS computation coupled with the equations of rigid body motion with full six degrees of freedom (6DOF), with a particular focus on the numerical modelling for a free-running CFD model. Ships are exposed to various environmental loads such as waves, wind, and currents during their operations at sea. Such external disturbances can lead to substantial changes in the behaviour of a ship during manoeuvring when compared to its inherent behaviour in calm water. Nevertheless, to date, the vast majority of studies in the field of ship manoeuvrability have been devoted to analysing the inherent manoeuvrability of a ship in calm water in conformity with the recommendation of ITTC. Their findings are not able to provide general observations on the relationship between external disturbances and manoeuvring behaviours. This thesis, therefore, aims to systematically carry out hydrodynamic analyses of a ship’s manoeuvring performance in different environmental conditions (including deep unrestricted water, regular waves, irregular waves, shallow water, and ocean currents) in order to provide an in-depth understanding of a ship’s manoeuvrability for navigational safety at sea. Firstly, a literature review of previous publications on all aspects of ship manoeuvrability is performed. The literature survey presents an overview of current standards and guidelines regarding the assessment of ship manoeuvrability, and then outlines a classification of the methods widely applied to manoeuvring problems. The research gaps detected during the literature review are also listed, which are addressed in detail in this PhD. thesis. Following this, free-running CFD models are developed for the prediction of the ship's manoeuvring performance by means of an unsteady RANS solver. These models are validated against the available experimental results from a free-running test. The numerical results are found to be in good agreement with available experimental data, which demonstrates that the numerical approach proposed in the present thesis is reliable in estimating ship manoeuvrability in various environmental conditions. Afterwards, a series of free-running CFD simulations are carried out to analyse the manoeuvrability of the ship characterised by a traditional single rudder / single propeller configuration in different environmental conditions. It is revealed that the environmental conditions applied in this thesis have a strong effect on the manoeuvring performance of the ship, including the hydrodynamic loads, kinematic parameters, turning indices, and trajectories through comparative analyses. Finally, the main results obtained from each chapter of this thesis are summarised and discussed, and recommendations for future work are made. It is highly believed that the general framework presented in this thesis could encourage academic researchers to participate in research on manoeuvring problems by performing free-running CFD simulations without much difficulty. It is also expected that the numerical results drawn from the hydrodynamic analyses in this thesis will provide navigators with a deeper insight into the ship manoeuvrability in real sea states as well as support them in proper decision-making for ship handling actions to avoid collision. In addition to this, the high-fidelity CFD model developed in this thesis can easily be combined with a path following algorithm for maritime autonomous surface ships (MASS), providing a valuable contribution to enhancing the safety of autonomous marine navigation.
Advisor / supervisor
  • Jeong, Byongug
  • Tezdogan, Tahsin
Resource Type