Numerical investigation of the seakeeping behavior of a polar vessel in head waves

Abstract

The SA Agulhas II plays a key role in logistical and research support in the Southern Ocean and Antarctica. It is estimated that open water transits account for 85% of her total voyages. As she is built to Polar Class PC5 with a thick rounded stem, it is expected that these characteristics will improve her performance in ice, but may lead to sharp increases in open-water resistance and affect other seakeeping aspects. In rough sea conditions, significant motions are induced, which subsequently leads to an increase in resistance and fuel consumption. Therefore, an investigation was undertaken to evaluate the seakeeping behaviour of the SA Agulhas II. Computational Fluid Dynamics was identified 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. 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 effective 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 effective power of 87%.