Benchmark Case Study of Scale Effect in Self-Propelled Container Ship Squat

A URANS CFD-based study has been undertaken to investigate scale effect in container ship squat. Initially, CFD studies were carried out for the model scale benchmarking squat cases of a self-propelled DTC container ship. In this study, a quasi-static modelling approach was adopted where the hull was fixed from sinking and trimming which is computationally more efficient than dynamic mesh methods that models actual motion directly. Instead, the quasi-static approach allows estimation of the squat base on the recorded hydrodynamic forces and moments. Propulsion of the vessel was modelled by the body-force actuator disc method. Upon successful verification and validation of the model scale self-propelled CFD model against benchmark data, full scale investigations were then undertaken. Validation of the full scale set-up was demonstrated by computing the full scale bare hull resistance in deep, laterally unrestricted water and comparing against the extrapolated resistance of model scale benchmark resistance data. Upon validating the setup, it was used to predict full scale ship squat in confined waters. The credibility of the full scale confined water model was checked by comparing vessel resistance in confined water against the Landweber empirical prediction. To quantify scale effect in ship squat predicitons, the benchmarking squat cases were computed by adopting the validated full scale CFD model with body-force propulsion. Comparison between the full scale CFD, model scale CFD and model scale benchmark EFD squat results demonstrates that scale effect is negligible.