Transient Fluid-Solid Interaction Characteristics Of The Water Entry Of Revolved Body Based On SPH Method

The issue of water entry is very important in the disciplines of naval architecture and ocean engineering and in the field of national defense.The water entry process of structures is accompanied by complex non-linear problems such as transient impact,liquid crushing,fluid splashing and climbing,gas-liquid mixing,and violent fluid-structure interaction.It often exhibits strong discontinuous characteristics.Also,the strong impact pressure always pose great threats to the strength and working performance of the structure,so the research on this topic has important scientific value and practical engineering significance.The structure's water entry process can generally be divided into impact phase,flow formation phase,open-cavity phase and closed-cavity phase.The whole process involves the difficult scientific problems of fluid compressibility,multiphase motion interface,and gas-liquid-solid coupling problem.In this study,through the in-house Smooth Particle Hydrodynamics(SPH)program,the impact load and cavitation flow during the water entry process are simulated,and the formation mechanism of impact load and the influence of related parameters,the flow characteristics of cavitation and other issues are explored.Based on the literature survey,the recent developments on the water entry are firstly briefly reviewed.Then we focus on the impact load and the cavitation flow characteristics,the shortcomings of the current research are determined.To solve the existing problems,the application research progress of the meshless SPH method in the water entry problems is reviewed,thus the meshless Lagrangian particle SPH method is selected.On this basis,regarding the features of water entry problem,the governing equations,the coupling interface treatment,and multi-level resolution algorithms are discussed,so an effective numerical research scheme for solving the water entry problem is formed.Based on the above theory,the fluid-solid coupling characteristics of a cylinder water entry are first studied.The impact load and the free surface flow characteristics of the vertical and oblique water entry are analyzed.Moreover,the influences of the injecting angle and velocity are considered.Then,a multiphase SPH model is established.After verifying its accuracy and reliability,the influence of air is taken into account.The air cushion effect and the influence of air compressibility are explored.Meanwhile,the influence of air on the flow of cavitation is given.After mastering the basic characteristics and rules of the air-liquid-solid coupling effect,finally the fluid-solid coupling characteristics of the three-dimensional revolved body water entry at a high velocity are carried out.The formation mechanism of the impact load and the development of the cavities represented,and then the effect of the rudder angle on the water entry progress is analyzed.