Numerical Analysis Of Impact Load And Flow Characteristics Of High Speed Water-entry For A Revolution Body Based On A Fluid-structure Interaction Method

The high-speed water entry process of cylinder bodies involves fluid and structure interaction,which is a complex nonlinear and unsteady process.The cylinder body with a high speed is subjected to extreme impact load at the moment of hitting the water surface which would cause great deformation or even damage to the structure.In order to investigate the physical understanding of the structural strength of cylinder bodies and the mechanism of the cavity dynamics during high-speed water entry process,a fluid-structure interaction(FSI)model based on a co-simulation progress between STAR-CCM+ and ABAQUS is adopted.The model performs a two-way interaction analysis.In the form of CFD analysis,a three-dimensional simulation with a six-degree-of-freedom model was carried out,where the Shear Stress Transfer(SST)turbulence model and the volume of fluid(VOF)technique were used for turbulence computation and air-liquid interface tracking,respectively.In the part of FEM research,the shell mesh form with a whole Johnson-Cook material model is implemented to give a full consideration of deformation process and the accuracy of solution.Firstly,this paper conducts a comparison between FSI result and experimental result of the high-speed water entry process.The results show that the velocity attenuation,displacement and the cavity features are in good agreement with the experimental result,which proves two-way FSI method can be effectively applied to the research of high-speed water entry problem.Subsequently,this paper carries out the numerical simulation of the high-speed water entry process of a cylinder at an inclined Angle.Compared with results of rigid body,the load peak of a flexible body appears smaller due to the repeated deformation for buffer,which also causes the fluctuation in the load curve.In addition,the hydrodynamic characteristics,cavity evolution,fluidity characteristics and structural dynamic response characteristics of cylinder bodies in the process of water entry are analyzed in the parametric researches of different velocities and head structures.For the further analysis of the dynamic response of structures,this paper continues to carry out the FSI simulation of the vertical water entry process including the structural analysis of stress,strain,deformation of cylinder bodies with different thickness,which provides a basis for the structural strength design.Besides,waves as a common ocean phenomenon whose motion will increase the complexityof the entry process and,for now most researches on water entry impact technology is focused on calm water condition.There is a lack of water entry researches considering the effect of waves.So this paper compares with theoretical results to verify the effectiveness of the wave model.In order to get close to the natural reality,this paper based on the FSI co-simulation method,carries out the numerical simulation of high-speed water entry on waves which includes the comparison with calm water condition and the fluid and structure analysis of the water entry process from different position of wave.