Blind Resistance Prediction Using CFD - A Summary of the Lucy Ashton Workshop

Other conference contribution, 2025

The confidence in using CFD for full-scale predictions is hampered by the lack of validation at full-scale, where measurements are much scarcer than at model-scale. In the 1950s, an experimental campaign was carried out on the "Lucy Ashton" paddle steamer, which was fitted with four jet engines on its deck for propulsion, thus avoiding the need for a propeller and consequently propeller-hull interaction effects. As a result, the "Lucy Ashton" experiments provide a rare and valuable opportunity that despite its merits is not well known in the maritime community. As part of the JoRes project, a blind CFD workshop based on the "Lucy Ashton" trials was organised and took place in 2024. This contribution provides an overview of the workshop, which received data from more than 40 different participants. Results for varying model-sizes at a constant Froude number, and variable Froude number at full-scale were received. Discrepancies in the reported resistance between participants were larger at model-scale rather than at full-scale, as a consequence of different approaches to handle the boundary-layer, i.e. wall-resolved vs wall-functions. The numerical results tended to underpredict the measured values since roughness was not considered and the simulations were carried out at even keel.