Numerical parametric study of medium sized container ship squat

Abstract

A numerical investigation has been undertaken to study the impact of varying a container ship's principal particulars on squat in shallow water. Initially, a statistical review of the principal particulars of commonly operating container ships is discussed and used to determine the range for length-to-beam ratio (L/B), beam-to-draft ratio (B/T) and block coefficient (CB) to be analysed systematically. Unsteady RANS CFD simulations are adopted to predict the squat of a self-propelled S175 container ship where the approach is successfully verifed and validated against benchmark experimental data. The same methodology is adapted to a KCS hull as a representation of modern container ships and systematic parametric transformations are conducted to study the effect of varying L/B, B/T and CB on squat. The results show that sinkage and trim are inversely related to L/B while sinkage is independent of B/T, but trim is inversely related to B/T. Sinkage is also found to be independent of CB whereas trim magnitude becomes increasingly stern down when CB increases due to the nature of the parametric transformations in this study. It is identified in this study that the relative position of the LCB to the LCF is responsible for the change in trim direction. Most empirical predictions show similar trends for varying L/B and B/T but contradicting trends are observed for varying CB.