Delayed detached eddy simulation method for breaking bow waves of a surface combatant model with different trim angle

Abstract

Sailing attitudes vary with different loading conditions for ships sailing in open sea, and the trim angle, either by bow or by stern, exerts considerable impact on the flow field around the ship. Currently, attention has primarily been focused on hull resistance and wave patterns while few studies have touched upon breaking bow wave under different trim conditions. This study aims to analyze the breaking bow wave of a surface combatant model with a length of 5.72 m DTMB (name of a surface combatant model) under different sailing attitudes at Fr = 0.35. The Delayed Detached Eddy Simulation (DDES) approach was adopted to study the breaking bow wave features such as plunging jet and air entrainment. The interface-compression algebraic Volume Of Fluid (VOF) method in OpenFOAM was used to capture the free surface. The Computational Fluid Dynamics (CFD) approach was firstly validated by comparing hull resistance and wave contour with the available experimental data. The study then delves into the influence of trim angles on breaking bow waves through simulations of the different conditions, i.e., 1 deg trim by bow, test condition and 1 deg trim by stern. The wave contour, breaking wave profile, vorticity field and the wake field at several transverse sections are then compared in three trim conditions, followed by an analysis of the initial evolution of bow wave breaking based on the turbulent kinetic energy and the vorticity field at four cross sections. The results suggest that trim by bow makes free surface sharper and wave amplitude larger in the breaking bow wave region. The reason is that trim by bow enlarges the attack angle of the bow, thus energizing the bow wave and generating a more violent free surface of bow wave breaking.