Investigation On Numerical Simulation And Semi-theoritical Formula Prediction Of Rotary Structure Water Entry Impact Motion Response

Structure entry problem is a typical engineering problem which is focused on by academic investigators.Water entry investigation of structure is widely applied in the area of aviation,aerospace,marine architecture and ocean engineering.Intensive impact load will appear as structure contacts with water surface in the entry duration.There is local damage or global destruction of structure because of the impact load.It is one of crucial technologies which is needed be mastered that predicting water entry trajectory and impact load accurately in water entry research.In the simulation investigation,coupled Eulerian-Lagrangian(CEL)analyses method was applied.Combined with the user redevelopment of Abaqus software,the numerical simulation of water entry process was completed.The influence regulation of initial attack angle,initial attitude angle,initial velocity value and wave-current load effect was analyzed.In order to avoid bottoming or structure destruction,the feasible method of reducing vertical displacement and acceleration load by adjusting initial condition factor was proposed,which aims at providing support reference for the structural design and the optimization of marine architecture and ocean engineering structures in the paper.First of all,based on the feature of rotary structure water entry,CEL method was chosen to be the simulation method for investigation of water entry.Rotary structure water entry impact response and cavitation were numerically simulated.Then,the simulation result was compared with experiment result and other simulation result to validate the efficiency of CEL method.What’s more,combining with redevelopment of Abaqus software,finite element numerical simulation model of rotary structure water entry was built,and rotary structure water entry analyses software was coded and complied.Secondly,the response characteristic of rotatory structure entry in still water was analyzed by CEL method.A typical condition of water entry was selected to describe the impact responses of structure in detail and typical phenomena in entry process were depicted.Then,the influence of initial attack angle,initial attitude angle and initial velocity value to impact response characteristics is investigated.Based on the time-domain response curves,the influence regulation of these factors of initial condition was summarized.Feasible method of reducing vertical displacement and peak of acceleration was proposed.Thirdly,based on the simulation results in still water shown before,the semi-theoritical formula prediction method of water entry impact response was proposed.According to the initial condition of structure entry,the velocity attenuation curve was predicted analytically.Besides,with the simulation results completed before,the influence regulation of initial velocity and initial attack angle was analyzed.Dimensionless velocity factor and dimensionless attack angle factor were calculated.Then,the prediction curve formulae of acceleration peak were attained.Combined the dimensionless velocity factor and the dimensionless attack angle factor,prediction curved surface formula was deducted.Finally,the response characteristic of rotatory structure entry in water with wave and current was analyzed.The influence of entry position and wave height towards response of structure was investigated when there is only wave motion existing.Also,the influence of current direction was analyzed with current load only.On the basis of the work of wave and current influence,combine wave with current together.The influence of complicate wave-current condition to structure response was carried out within the project.This work can provide feasible plan which is used for reducing vertical displacement and acceleration peak in structure design.