Session: 06-12-01 Ship Hydromechanics I

Paper Number: 78937

78937 - A Fast and Transparent Method for Setting Powering Margins in Ship Design 

Traditionally, a ship is designed to achieve her design speed in ideal weather conditions at certain power output, as typically specified in the shipbuilding contract. Based on this, a sea margin and a light running margin (LRM) are added to the required power in calm water as a provision to meet the increased power demand of a ship in operation caused by wind, wave, fouling of hull and propeller, etc. (ITTC, 2008). On modern ships, a sea margin of 10-25% and a LRM of 4-10% are typically applied (MAN, 2015). Typically, the specific values are agreed in the shipbuilding contract between designer and owner. This kind of practice in selection of powering margins is not optimal (ABB, 2021) and should be optimized in the preliminary ship design stage. Nowadays, more ship operational data have been recorded and alternative methods have been developed to facilitate the fast and transparent calculations required by such a task. In this work, the influence of wind on ship resistance is calculated using the methods recommended by ITTC (2021). The influence of wave on resistance is calculated using the method of Liu and Papanikolaou (2020), which is also recommended by ITTC (2021). The influence of fouling on resistance is predicted by the method of Granville (Granville,1958; Schultz, 2007) while the influence of fouling on propeller performance is predicted by the method recommended ITTC (1978). All the implemented methods have a strong root in theoretical and experimental studies, are easy-to-use and are fast in execution. A case study is presented to demonstrate the methodology. This work aims to support designers in the selection of proper powering margins in the frame of preliminary ship design and the selection of ship’s machine and propulsion system to meet the more and more stringent regulations in relation to the safe and efficient ship operations.

Presenting Author: Shukui Liu Nanyang Technological University

Authors:

Shukui Liu Nanyang Technological University
Baoguo Shang Marine Design and Research Institute of China
Haoliang Chen akzonobel
Apostolos Papanikolaou National Technical University of Athens