Numerical Simulation Of Ship Bow Wave Breaking Under High Speeds

Wave breaking always occurs at bow of high speed ship,the research of ship bow wave breaking has following meanings.Firstly,the turbulence generated by breaking will flow to the wake field,causing energy dissipation and wave breaking resistance.Secondly,the wave plunging is usually accompanied with air entrainment and splashing,forming white water wake,bubble flow and inducing underwater noise,which affects the sonar system of ship.Therefore,the research of bow wave breaking is of great importance for warships with high concealment requirements.This master dissertation focuses on the numerical simulation of ship bow wave breaking using ship hydrodynamic solver naoe-FOAM-SJTU.In this paper,the volume of fluid method VOF is employed to capture the liquid-gas surface.RANS and DDES models are used to simulate the wave breaking.In order to verify the feasibility of the numerical model in simulating wave breaking,flow-opposite two dimentional plunging wave breaking is firstly calculated.Based on RANS model,the evolution and changes of flow field of 2D plunging wave are analyzed as well as the spatiotemporal characteristics under different velocities.In addition,DDES model is applied to the simulation of plunging breaking and the result is compared with result of other models.The 3D bow wave breaking is significantly influenced by ship speed.Based on RANS model,the simulation of bow wave breaking of KCS model at fixed condition under different speeds is conduted in this paper.The bow wave structure,air entrainment and flow field changes at different speeds are analyzed.In order to study the influence of ship posture on bow wave breaking,the bow wave structure and wave parrern of fixed condition and free condition are compared at Fr（28）0.35 in this thesis.The DDES model is also used to simulate the ship bow wave breaking.In order to verify the reliability of grid disturbution and numerical model,the results of bow wave structure and wave height simulated by DDES and RANS are compared with experimental data.In addition,the bow wave structure,velocity and vorticity calcuted by DDES and RANS are compared to figure out the influence of turbulence model on wave breaking.