Fully Nonlinear Simulation For Free Water Entry Of 3D Cones Into Stokes Waves

The slamming phenomenon is a phenomenon that often poses a great threat to the hull safety during the voyage of a ship.When slamming occurs,the severe fluid-structure interaction may cause the hull to be damaged,which can cause slamming loads during the voyage.Prediction of slamming load during hull voyage is an essential part of ship design.However,the existing slamming load prediction methods are not perfect,and empirical formulas are used for forecasting in actual work.Therefore,it is of great research and application significance to develop a fully nonlinear numerical simulation method that takes into account the complex nonlinear factors in the slamming process.Based on the potential flow theory and the boundary element method,a fully nonlinear numerical simulation program for simulating the three degree of freedom free entry process of an object in the time domain is developed.Green's third equation is discreted to facilitate numerical calculations.Auxiliary function method and boundary element method are applied to solve the fluid-solid interaction problem in the process of entering water to determine the motion and force of the object.A telescopic coordinate system is adopted to adapt the grid to the rapidly changing wet surface area.The non-linearity of the free surface is considered when updating the free surface in the time domain numerically.The fifth-order Stokes waves are used as the incident waves,and their equations are used to determine the boundary conditions.In the process of numerical calculation,a smoothing algorithm is used to smooth the grid to reduce the cumulative error caused by numerical calculation and improve the stability of numerical simulationThis paper uses Fortran language to complete the development of a numerical simulation program for free fall water entry of a 3D object,and simulates a one degree of freedom free fall process and a three degree of freedom free fall process of a cone in waves and still water.In this paper,the convergence step of the calculation program is analyzed to determine the integration step size of the calculation program.Contrast analysis of the water entry process at different wave heights,and analysis of the impact of incident wave height on the free water entry process;water entry processes of cones with different initial horizontal velocities,cones with different initial vertical velocities and cones with different densities were simulated,and the differences between the different water entry processes were analyzed,and the characteristics of the water entry process were included.