MDL

Research on predicting ship performance in waves

Traditionally, contracts between shipyards and shipowners are based on the fulfilment of a single contractual point, namely that a ship achieves a certain speed with a given engine power in calm water. Such a one-sided approach can obviously result in the ship performing poorly in off-design conditions. It is for this reason that the current focus seems to have moved away from that single contractual point and towards operational profiles, design for overall performance and the ability of a ship to fulfil a certain transport task in a given time. This paradigm shift is closely related to today’s emphasis on energy-efficient shipping, slow steaming and route optimisation.

Modern ships are now designed to perform well in a range of realistic conditions rather than merely in calm water. Consequently, performance predictions under the influence of wave and wind loads are becoming more and more important. This in combination with the introduction of the Energy Efficiency Design Index (EEDI) has resulted in numerous ideas such as improved bow shapes to reduce “added resistance” in waves. The International Maritime Organization (IMO) has also introduced guidelines to determine the minimum propulsion power that can be used to maintain the manoeuvrability of ships in adverse conditions.

Our experts find that manoeuvring and seakeeping performance generally features too late in the design process and that sometimes the shipyards have to make costly and timeconsuming last-minute changes to the design if the standards for ship manoeuvrability are not met or seakeeping performance is poor. All these developments increase the demand for ship manoeuvring and seakeeping performance with higher accuracy than before, and stipulate new and more stringent requirements for testing techniques and evaluation methods.

SSPA is now conducting a research project to increase the accuracy and efficiency of detecting added resistance in waves experimentally and numerically. More accurate and efficient numerical and experimental procedures will make it possible to cost-effectively predict overall ship performance in a seaway early during the design process and to avoid costly pitfalls.

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