Study On The Vibration Response And Reliability-Based Design Optimization Of Bow Structure Under Bow Thruster’s Excitation

With the higher requirements of modern ship’s maneuverability,bow thrusters are wildly used on ships.However,it needs to pay attention that vibration responses caused by the propeller when it works is not negligible.In the process of ship design,designers hope that the ship can satisfy the requirements of classification societies and save materials as far as possible.And optimized design of structure is an effective method to solve this problem.The processes of assessment of vibration responses of ship structures with bow thruster and reliability-based optimization of ship structures are proposed in the view of engineering.In order to analyze the influence of excitation of bow thruster for ship structures,Fluent is used to calculate the time-domain bearing force and pulsating pressure.And Delaunay triangulation interpolation method and Fourier transform are used to obtain frequency-domain loads of finite element model.Nastran’s dynamic module is called to complete frequency response analysis.Finally,the influences of amplitude and phase of bearing force and pulsating pressure are discussed.The problem of reliability-based design optimization of ship structures is studied,considering uncertainty of design variables.In order to overcome the difficulty that balance between efficiency and accuracy in traditional methods is hard to keep,a process of reliability-based design optimization of ship structures is established for huge ship FEM models by synthesizing particle swarm optimization(PSO)and ensemble of surrogates with recursive arithmetic average(ER)into sequential optimization and reliability assessment(SORA)method.The optimization results show that reliability-based design optimization is more meaningful than deterministic optimization in practice.And the improved process guarantees the high accuracy of solutions and significantly reduces the computational cost.