Research On Hull Structural Dynamic Response Under Slamming Loads

While ships sail in bad sea condition,heavy slamming phenomenon will happen between the hull and waves because of the pitch and heave motion of ships.Slamming will not only damage local structure,but also destroy the longitudinal strength and lead to the loss of personnel and property.In recent years,with the innovation of shipbuilding technology and the need of ocean oil and gas resources exploiting,all kinds of ships continually develop into high-speed and large-scale,which will cause more slamming problems.Therefore,it is required that hull structure slamming loads prediction and dynamic response analysis be rationally carried out because these have gradually become important foundations of hull design optimization and new slam-resistance structure.This thesis is based on pre-research fund supported project of ship industry,which adopts the method that combined simulation calculation and model test to carry out the hull structure slamming loads prediction and dynamic response analysis.It analyzes the influence rule of different parameters on slamming loads and dynamic response of structure and discusses the effect of rigid and elastic structure on slamming loads prediction.Then,it takes bow flare plated grillage and the whole bow as the research objects and analyses the dynamic response of structure under typical slamming scenarios.The main contents of this paper are as follows:(1)The classical theoretical calculation method on water entry of structure is summarized and the thoughts as well as applicable scope of these methods are cleared.At the same time,the basic principle of Arbitrary Lagrangian-Eulerian(ALE)method is introduced.On this basis,the key technology of numerical simulation is presented.(2)The tests of 2D and 3D structures slamming into the water are carried out and the pressure distribution at different measure points is obtained.It is making contrastive analysis about the influence rule of different deadrise angles and different entry velocities on slamming pressure.Three dimensional effects are discussed deeply and the slamming characteristics of structures are assessed comprehensively.The above work provides the basis for verification and improvement of the numerical simulation method.(3)The large finite element software ANSYS/LS-DYNA is used in this paper to conduct numerical simulation calculation for the water entry of 2D and 3D test models.The effect of different deadrise angles and different entry velocities on slamming pressure and vertical force are analyzed.The contrastive analysis between the numerical simulation results and the test results verifies the reliability of the simulation technology and slamming loads prediction method.(4)Based on the slamming test and slamming loads prediction,the finite element models of 2D elastic wedges and 3D elastic cone are established.According to the numerical simulation results,the dynamic response of 2D and 3D structure are analyzed,the influence rule of different parameters on dynamic response of structure is summarized and the hydroelastic effect on slamming pressure is discussed.These will lay the foundation for the analysis of hull structure dynamic response in subsequent work.(5)This paper chooses the typical bow flare slamming and bottom slamming scenarios and determines the simplified bow flare model and the whole bow model to study the dynamic response of water entry of structure.In this paper,the influence rule of slamming pressure on dynamic response is discussed and the slamming pressure and dynamic response of structure under different stiffness are also analyzed.The influence rule of stiffness variety on dynamic response of structure will provide a reference for the design of structure.