Browsing by Author "Van Zuydam, Armand"

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    An investigation of the seakeeping behaviour of a polar vessel in waves
    (Stellenbosch : Stellenbosch University, 2021-03) Van Zuydam, Armand; Bekker, Annie; Meyer, C. J.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.
    ENGLISH ABSTRACT: The SA Agulhas II plays a crucial role in logistical and research support in the Southern Ocean and Antarctica. It is estimated that open water transits account for up to 85 % of her total voyages. She is built to Polar Class PC5 with a thick rounded stem and a full fore-body. Instinctively, these characteristics improve her performance in ice but may lead to sharp increases in open-water resistance and a ect other seakeeping aspects. In particular, her spoon-shaped bow and at raised transom predispose her to slamming. In rough sea conditions, signi cant motions are induced, which subsequently leads to an increase in resistance and fuel consumption. To ensure e cient performance at sea, vessel owners must have knowledge about a ship's responses in these environments. Therefore, an investigation was undertaken to evaluate the seakeeping behaviour of the SA Agulhas II. Full-scale measurements were conducted onboard the vessel during a cruise in the Southern Ocean. Data obtained from this campaign were used to determine the heave, roll and pitch motion responses in irregular waves. Strip theory was implemented to determine the motion Response Amplitude Operators of the vessel. Through superposition of the Response Amplitude Operators and the wave spectrum, the motion responses in irregular waves were predicted. A comparison between measured and predicted motion responses showed that heave and pitch could be predicted with reasonable accuracy. Roll motion showed various discrepancies and future research is recommended to study non-linear e ects, such as roll damping. Computational Fluid Dynamics was identi ed as an essential tool to investigate her motion responses and added resistance in head waves. During this work, three speeds were evaluated, her design speed of 14 kn, a reduced speed of 10 kn, and an increased speed of 18 kn. Overall, the results showed that the maximum heave and pitch motions are expected to occur when the encounter frequency ranges between 0.124-0.143 Hz. For all three speeds, the maximum added resistance in waves was observed when large-amplitude motion occurs. It was further shown that a reduction of speed from 14 kn to 10 kn could decrease her e ective power by 42 %. On the other hand, increasing speed by 4 kn from 14 kn to 18 kn could lead to a maximum increase in e ective power of 87 %. Computational Fluid Dynamics investigations further showed that slamming could occur at the bow region of the SA Agulhas II even though she is not operating in extreme conditions. Computational Fluid Dynamics shows clear potential for further investigations into bow and stern slamming for the SA Agulhas II.