Research On Impact Characteristics Of Vertical Water Entry Of A Structure

In this thesis, the impact of a structure dropping vertically into the water is analyzed throughboth numerical simulation and experiment. Some foundation is laid for the prediction of the impactdamages of shell structures in water entry process. The numerical methods forged and the resultsobtained can serve as reference for the strength and buffer design of these kinds of structures. Themain work accomplished in the thesis is as follows.Firstly, each stage of the water-entry process is described, according to the impact phenomena,and the research status of the problem is reviewed. The essential related theories concerning thewater-entry impact are explained, including the classification, the basic knowledge of the fluidmechanics, the basic theory of the finite element and the basic knowledge of the numerical simulationfor the couple of liquid-solid problem.Secondly, the detailed simulation process of the structure impact into the water is analyzed. Theprocess includes the establishment of the structure and the fluid model, the definition of the materialparameter, the division of the model mesh and the determination of the mesh size ratio, the definition ofthe initial conditions and boundary conditions. We deeply researched the influence of variousparameters to the simulation results in the computing process. It is found that to obtain a reliable resultsome key factors in the modeling process is of vital importance.In the end, an experiment for a cylindrical tube dropping into the water from a certain height isconducted, and the impact acceleration data of the bottom of the tube is acquired. The error analysis ofthe experiment results shows that the experiment results don’t have larger deviation, and the data isscientifically rational. From the results, it’s clear that the acceleration peaks in both simulation and thetest are well matched, and the reliability of the established numerical simulation method is verified.