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Abstract

Mathematical models of manoeuvring ships need to be developed both to assist in the design of training simulators and autopilots and also as an aid to understanding the behaviour of ships themselves. In this thesis the range of existing models is examined and their limitations discussed. The principal limitation found is their inability adequately to simulate manoeuvring behaviour over the extremely wide range of operating conditions found in practice.

A new approach to simulating manoeuvring ships is developed, by considering the hull as an inclined foil surface and examining the forces and moments acting on it. This direct method does not require the linearisation inherent in many conventional models and is therefore particularly suited to the simulation of directionally unstable ships. Wind tunnel experiments have been used to help to visualise the shape of the flow over the hull. The nature of the complex flow around the stern of the hull and in the area of the propeller is considered and simulated using largely empirical techniques.

The model is evaluated by comparing its manoeuvring behaviour with that of two widely different ships, a 200 000 tonne Very Large Crude Carrier, (VLCC), and a 20 000 tonne fast cargo ship, for both of which extensive
manoeuvring trial data are available. A comprehensive suite of digital and analogue computer programs is developed to assist in the quantitative evaluation of the model using conventional optimisation techniques. It is
found that the model is well able to simulate a variety of ships over the whole range of ship speed, ship draught and water depth encountered in service. As operating conditions change only those parameters logically associated with the changed physical conditions need to be altered for the model to continue to represent ship behaviour.

The importance of the drift angle as a state variable in the study of manoeuvring ships is stressed and methods of measuring it with sufficient accuracy discussed. The extension of the model to enable marine vehicles with six degrees of freedom, such as submarines and submersibles, to be simulated is finally considered.

Publication Type:	Thesis (Doctoral)
Subjects:	Q Science Q Science > QA Mathematics T Technology > TC Hydraulic engineering. Ocean engineering V Naval Science > VM Naval architecture. Shipbuilding. Marine engineering
Departments:	School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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