A Look at the Full Picture of Speed-Power Predictions from Model Tests and CFD Simulations

In the design process of a new vessel, ship speed-power predictions provide designers valuable insight regarding the expected performance of the vessel with respect to the contractual speed requirements. In this study, two different methods for acquiring this speed-power prediction, being model tests and full-scale Computational Fluid Dynamics (CFD) simulations, are compared for a bulk carrier with an open Controllable Pitch Propeller (CPP) and a general cargo vessel with a ducted CPP. Both approaches are compared to ballast sea trial data and it is shown that the two methods can lead to significantly different predictions, especially when the sea trial results are used to scale the speed-power curves from either method at ballast draught to design draught. As the fuel consumption and carbon intensity estimations are based on the speed-power curves, the impact of both methods on the International Maritime Organization’s (IMO) Energy Efficiency Design Index (EEDI) regulations is evaluated. It is argued that a suitable, accurate, and consistent prediction method is required for all propulsion types to meet the ever-increasing real-world performance targets that are being set by ship owners, governments, and other regulating bodies.