Numerical investigation on nonlinear ship waves by LCM and WSAM

Abstract

This paper investigates the nonlinear ship waves by implementing the longitudinal cut method (LCM) and wake survey analysis method (WSAM) in the computational fluid dynamics (CFD) simulation. LCM is first implemented and validated for a Series 60, Cb = 0.6 ship model to guarantee accurate prediction of the wave pattern resistance (Rwp). To illustrate the reliability, WSAM is performed for a wall-sided model, incorporating the local adaptive mesh refinement (LAMR) and surface tension models to capture nonlinear bow waves. Far and near-field wave patterns and momentum loss resistance (RML) are compared with the experiment.With the well-predicted nonlinear bow waves, the velocity discontinuity property across the nonlinear wavefront and the vortex motion beneath the nonlinear waves are clearly observed by velocity vector and Q-criteria iso-surface visualization. By LCM and WSAM analysis, the discrepancy between wave resistance (Rw) and Rwp is attributed to the nonlinearity in ship waves, and expression to evaluate this part of resistance (Rnw) is discussed and summarized. Finally, the influence of velocity and draft on Rnw and bow wave angle (β) is systematically analyzed and discussed. This study hopes to provide insights to evaluate the nonlinearity in ship waves and further understand its underlying mechanism.