Research On The Strong Nonlinear Ship Slamming Load Based On CFD Technology

As one of the key research interests in Naval Architecture and Ocean Engineering,ship slamming in waves has the property of nonlinearity.Fierce slamming may reduce the fatigue strength of the ship and cause severe damage to the hull structure.Therefore,during the ship design process,slamming loads should be considered to ensure,the ship safety.In this paper,the strong-nonlinear-slamming numerical model of ship is established by the ommercial softwar STAR-CCM+(hereinafter abbreviated to STAR),which is based on the CFD solver.Beginning with the simplified wedge,the numerical simulation of its water entry problem is carried out.To verify the reliability of the model,the numerical results are compared to the self-similar solutions and the previous experimental results,and then the shallow-water-entry problem are discussed.Compared to the simplified wedge,the ship profile model can reflect better slamming mechanism,and is typically preciser.However,the unified simplified ship profile model is generally used in the prediction of the ship hydrodynamic characteristics.Considering the different shapes of ship profiles at different positions,the hydrodynamic characteristics of several simplified profile and the original bow profile are studied in detail,such as vertical slamming loads and the free surface elevation.Finally,in order to further study the real ship slamming phenomena,the strong-nonlinear-slamming problem of the container ships in large wave height is carried out.After verifying the numerical waves,the slamming phenomenon of three-dimensional hull under different working conditions,such as the head wave and different oblique waves are dicussed.The following research content are carried out in this paper:(1)The finite volume method,VOF method and overset mesh used in this paper are introduced,in which the governing equation,interpolation methods and the selection of different physical models in different chapters are carried out in detail.(2)Considering the complexity of the slamming problem,the numerical model of the water entry problem of wedge is established to analyze the influence of the deadrise angle on the impact force,pressure and free surface elevation.The effect of shallow water was analyzed,and the dimensionless ratio Rp was introduced to quantify the effect of end wall on dimensionless pressure.Rr was introduced to quantify the effect of the bottom on wet length.The dimensionless force Cs was introduced to investigate the influence pattern of different water depth on the impact force of the wedge.(3)Based on the ship profiles in published papers,the numerical models of water impact of different ship profiles are established.The differences of hydrodynamic characteristics between the original bow section and simplified sections,including slamming force,free surface elevation and pressure,are studied in detail.The reasons of the differences are also analyzed,which provides the basis for the section selection for tank tests.(4)Refering to the wave data in the published paper,numerical wave simulations in two different wave heights are carried out to verify their accuracy.Then,the simulation of a 6750-TEU container ship in a certain large wave high-altitude is carried out according to the verified numerical wave generation technology,which is compared with the experimental and numerical results in previous papers.Finally,according to the different angles between wave direction and ship direction,the characteristics and patterns of the ship’s slamming load under the conditions of head wave,20° oblique wave and 45°oblique wave are analyzed by using the verified model.