Full-Scale Resistance Prediction in Finite Waters – A Study Using CFD Simulations, Model Test Experiments and Sea Trial Measurements

The development of large medium-speed catamarans aims increasing economic viability and reducing the possible negative influence on the environment of fast sea transportation. These vessels are likely to operate at hump speed where wave-making can be the dominating component of the total resistance. Shallow water may considerably amplify the wave-making and hence the overall drag force. Computational fluid dynamics (CFD) is used to predict the drag force of medium-speed catamarans at model and full scale in infinite and restricted water to study the impact on the resistance. Steady and unsteady shallow water e↵ects that occur in model testing or full-scale operation are taken into account using CFD as they are inherently included in the mathematical formulations. Unsteady e↵ects in the ship model response were recorded in model test experiments, CFD simulations and full-scale measurements and found to agree with each other. For a medium-speed catamaran in water that is restricted in width and depth, it was found that CFD is capable of accurately predicting the drag with a maximum deviation of no more than 6% when comparing to experimental results in model scale. The influences of restricted depth and width were studied using CFD where steady finite width e↵ects in shallow water and finite depth e↵ects at finite width were quantified. Full-scale drag from CFD predictions in shallow water (h/L = 0.12 0.17) were found to be between full-scale measurements and extrapolated model test results. Finally, it is shown that current extrapolation procedures for shallow water model tests over-estimate residuary resistance by up to 12% and underestimate frictional forces by up to 35% when compared to validated CFD results. This study concludes that CFD is a versatile tool to predict the full-scale ship resistance to a more accurate extent than extrapolation model test data and can also be utilised to estimate model sizes that keep finite water e↵ects to an agreed minimum.