Research On The Method For Estimating The Slamming Load Of Hovercraft

As all countries in the world attach importance to the ocean and human beings develop marine resources,the industry of naval architecture and ocean engineering is becoming more and more important,and the defense of China’s coastline has gradually become a key military issue.China’s coastline is very long,and landing conditions are also very different,so the role of hovercraft with strong amphibious landing ability is increasingly prominent.In addition,the hovercraft also plays a very important role in civil applications such as sightseeing and tourism.Due to the high speed,hovercrafts will be subjected to larger slamming load in rough conditions.At present,most researches on calculation methods of hovercraft’s slamming load focus on the slamming problem of rigid hull and water surface.However,most of the slamming load encountered by hovercraft does not directly act on the rigid hull,but is transmitted through the air cushion and skirt airbags on the bottom of the ship.In this thesis,a method is proposed for estimating the slamming load accounting for the influence of air cushion and airbag.The main research contents of this thesis include:(1)The basic theories of control volume method,symmetrical penalty function method and ALE fluid structure coupling method are briefly introduced.The control volume method is based on the adiabatic gas equation of state and assumes that the gas inside the skirt of the hovercraft is uniform.ALE fluid structure coupling method combines the advantages of Lagrange method and Eulerian method,which can simulate the slamming process of hovercraft.(2)The slamming load calculation method proposed in this thesis is verified for the cases of simple structure landing on rigid ground,simple structure slamming on water,complex structure landing.To validate for the case of a hovercraft,a model test is also carried out,and the numerical results are compared with the experimental ones.(3)The slamming process of air cushion landing on rigid ground is studied,and the motion parameters,skirt parameters and mechanical parameters of hovercraft are obtained.In the process of simulation,3 different configurations of bag are investigated: bag without air orifices,bag with air orifices but no air flows,and bag with air orifices and air flows.(4)The slamming of air cushion on still water surface is studied.After establishing the fluid domain and configuring the parameters of fluid structure coupling,3 different skirts of hovercraft are explored and analyzed.Then,the motion parameters,skirt parameters and mechanical parameters of the hovercraft are analyzed.Finally,the parameters obtained from the slamming of hovercraft and rigid ground are compared with the case of slamming on still water surface.