Multiple Approaches to Numerical Modeling of Container Ship Squat in Confined Water

Abstract

Various URANS modelling techniques to predict container ship squat in confined water are investigated and compared in this study to assess the suitability of each modelling technique. Five methods are compared, among which three are quasi-statical estimations of squat from CFD computed hydrodynamic forces and moment (QS), and two are based on directly computed squat utilising dynamic overset meshing (OV) technique. In addition, the effect of self-propulsion on squat is investigated by comparing different methods of propulsion i.e. the hull is either towed (T) or self-propelled by means of body-force propulsion virtual disc model (VD) or a fully discretised propeller (DP). The investigation shows that the QS methods tend to be superior in terms of computation efficiency, range of applicability and trim prediction accuracy. It is also shown that the effect of self-propulsion is significant and should be accounted for to provide accurate results, especially at relatively high speeds. Moreover, virtual disc modelling is more computationally economical while also providing similar degree of accuracy to that of a discretised propeller. Thus, the most suitable method is the quasi-static method with virtual disc self-propulsion (QS-VD). However, for very shallow cases where h/T < 1.14, the towed quasi-static squat model (QS-T) is recommended due to better accuracy.