CFD approach to full-scale resistance: The Lucy Ashton case

Accurate prediction of ship resistance remains a major challenge in Computational Fluid Dynamics (CFD), particularly when translating results from model to full scale. This study investigates the prediction of total resistance for the historic vessel Lucy Ashton using CFD across six model scales and full scale. Experimental resistance data were harmonized using third-order polynomial fits, enabling consistent comparison with CFD results. Two full-scale approaches were evaluated: Setup 1 with prescribed inflow and Setup 2 incorporating surge motion with applied thrust to emulate deck-mounted jets used during sea trials. Across all scales, CFD predictions showed strong agreement with experiments, with deviations typically within ±5%, consistent with accepted validation standards. Dynamic motions (heave and pitch) were also examined, and both setups produced nearly identical trends, with absolute differences negligible for resistance assessment. The results demonstrate that both CFD methodologies provide reliable full-scale resistance estimates.