Evaluation of Ship Resistance and Seakeeping Performance of a High Speed Trimaran for the Pre-salt Layer in Brazil

Abstract

The offshore oil exploration in the pre-salt layer of Brazil is performed in ultra-deep water (above 2000 m) at 200 NM from the coast. The large distance from the coast provides a large downtime for the OSV (Offshore Supply Vessels) operations due to crew exchange, which is also increased due to port’s queue. The application of High Speed Vessels (HSV) as a crew boat to support offshore operations is a challenge since the required speed (above 25 knots) provides a large fuel consumption, which could be optimized by reducing the displacement, wetted surface and considering a multi-hull concept. However, the low displacement of these solutions usually provides a bad seakeeping performance, mainly under the harsh environmental conditions of Santos Basin. A large trimaran concept is proposed to support this mission, which requires an accurate prediction of either ship resistance or seakeeping performance in order to achieve the required uptime. A large experimental campaign was performed at IPT towing tank in the presence and absence of waves for the evaluation of calm water resistance, added resistance and seakeeping considering some pre-established conditions. The experimental data is applied to validate the Finite Volume Methods model to predict ship resistance in calm water, which is combined to the estimative of added resistance using strip theory and BEM to obtain the total ship resistance. The seakeeping performance is also validated using experimental data regarding regular waves and extended to irregular sea state conditions using spectral theory. The numerical models are applied to estimate the vessel performance considering the entire metocean conditions of Santos Basin providing the expected uptime.