Resistance and powering prediction using AutoPower module of AutoShip software case study

In the preliminary design stage of displacement ships, assessing total resistance and propulsion power demand is critical, since variations in hull form parameters significantly influence propulsion efficiency and engine sizing. In this study, the AutoPower module of the AutoShip software suite is used for a monohull vessel and a catamaran with a symmetric hull, both having similar main dimensions. Resistance and effective power were computed for a speed range between 0 and 22 knots using several empirical methods implemented in AutoPower, including Andersen/Guldhammer, Holtrop, van Oortmerssen, Digernes/Cheng, and Fung. The results highlight significant variations between the methods, with effective power predictions at the service speed of 18 knots ranging from 3.5 kW (Holtrop) to over 20 kW (Digernes/Cheng). The originality of the paper lies in emphasizing both the usefulness and the limitations of empirical formulations in the preliminary design of ships. The study concludes that, although AutoPower provides a fast and practical framework for estimating power requirements, the choice of prediction method must be correlated with the ship type and hull characteristics, while validation through model tests in hydrodynamic towing tanks or CFD simulations remains essential to ensure reliability.