Influence of drift angle on the self-propelled ship’s powering performance in waves

Abstract

The ability to accurately predict the ship's powering and manoeuvring performance in waves is of high importance for the design of new vessels. This is closely related to ship safety, reliability, and overall propulsive efficiency. However, it is a challenging task because of the complex interaction among ship motions, wakefield, and hydrodynamic forces exerted on the hull and its appendages. Conventional experimental methods and direct numerical simulation of dynamic manoeuvring in waves can provide valuable results, but both of them are very costly and time-consuming. Besides, the validation of traditional direct ship manoeuvring calculations is still very difficult and expensive. Therefore, a more cost-effective numerical method to accurately predict the powering and manoeuvring performance of ships in waves is still in high demand. Instead of modelling the complete time-varying manoeuvre, this thesis presents a cost-effective numerical approach for evaluating the fully appended ship under static drift, static rudder and combined drift rudder conditions, representing quasi-static phases of actual ship manoeuvre in waves. A stepwise study procedure is used including the double body method and the Volume of Fluid free surface calculations in calm water and waves. Two body force models are used for propeller modelling in drift conditions and the sectorial approach of Blade element momentum theory is adopted to capture non-uniform wake. The computed results are compared to available experimental and numerical results. The hull forces in some drift computations are validated with EFD data from the Southampton Boldrewood towing tank. This provides a reference for experimental measurements of hull and appendage forces and contributes to future validation of actual dynamic manoeuvring simulation. The presented methodology and results of drift influence on fully appended ships allow for the integration of wind-assist devices on commercial ships and predict the interaction between wind propulsion systems and ship hydrodynamics for wind-assist ships, thereby contributing to reducing fuel consumption and related emissions from ships and realizing the goal of decarbonisation in the maritime sector.

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Identifiers

ORCID for Yifu Zhang: orcid.org/0000-0001-6980-3985

ORCID for Stephen Turnock: orcid.org/0000-0001-6288-0400

ORCID for Dominic Hudson: orcid.org/0000-0002-2012-6255

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