Slamming Load And Response Study Including Structural Elasticity Effects

It is unavoidable that slamming phenomenon happens on the ship and ocean structures during their long service life in harsh working environment. In general, the rules and codes take the hull as a rigid body to calculate the impact load by some effective experimental or numerical methods. Then the load is used to evaluate strength of impacted region. But, the real structure is deformable when it is subjected to high magnitude pressure. The interaction of body and fluid plays a considerable role in the synchronous slamming period. Therefore, a conservative way maybe utilized if these coupling reactions are neglected under the rigid body assumption. For this reason, the following problems are emphatically investigated.Firstly, a group of coupling differential equations were deducted based on Wagner simplified method. Galevkin method was used to solve the deformation of wedge structure. Wagner's flat plate fitting velocity potential was amended to perform numerical analysis. A group of elastic wedges'slamming pressure was analyzed by the numerical program. The influence of structural elasticity on slamming load was summarized and some wedge related parameters'effects were discussed also.Secondly, water entry of a series of elastic wedge models was simulated. The results show that, elasticity of structures not only reduces pressure magnitude contrasting against rigid body water entry, but also changes locations of the impacting peak pressure. The pressure time history has a wave characteristic. Smaller deadrise angles, lower entry velocity and thinner plate give more considerable elasticity influence on transient slamming pressure.Secondly again, the model of jet impacting elastic plate was investigate to explore the load effect. In the initial period of impact, a lower magnitude pressure was produced, then the second pressure wave peak followed with a considerably notable value. Induced pressures on the extended free liquid surface also have a considerable magnitude after the initial period. For validation of related theories, free surface variation and shock wave propagation were researched against some resumes of related theories, which suppose that the free surface is changeless and the shock wave propagations velocity is on the assumption of velocity of the sound in the water.Finally, a simplified method is proposed to solve the elastic-plastic buckling of beam under slamming load. The difference with previous study is that, the real experimental measurement of slamming pressure history and the experimental material constitutive equation were utilized in this thesis. The influences of initial geometric imperfections, duration of pressure loads were investigated and finally some conclusions are reached.