The Numerical Simulation Of Cavitation Effects On Response Of Marine Structure Subjected To Underwater Explosion

As well as shock waves and bubble pulse loading, another effect, that is cavitation (local cavitation and bulk cavitation), has a very significant influence on the response of surface ships and other near-surface marine structures subjected to underwater explosion. A high reloading pressure is generated within at huge cavitated region closure, known as bulk cavitation closure. Cavitation effect cannot be ignored, and it is necessary to investigate cavitation effects on the response of near-free-surface structures.In this thesis, cavitation caused by non-contact underwater explosion is investigated. A cavitating acoustic finite element method contained in ABAQUS is introduced, which can numerically simulate the responses of simple structures and whole ships subjected to underwater explosion with cavitation effects.The response of a ship-model subjected to far-fluid underwater shock and the deformation of the model subjected to near-fluid underwater shock are simulated. The simulation results agree well with the measured results. It's proved that the numerical method can simulate the response of structures subjected to underwater shock wave very well.The development and closure of bulk cavitation and local cavitation are numerically simulated. The simulation results agree well with the experimental results, which proves that the numerical method can be used for simulation of cavitation. Simulation results shows that a secondary pressure wave is produced in the fluid near the cavitation closure point, and structure nearby is reloaded. The duration of reloading is several times longer than the duration of shock wave.Dynamic response of a surface ship subjected to underwater explosion is simulated. The response of the hull structure considering cavitation is compared with the structural response without cavitation effects. The secondary loading on the ship caused by bulk cavitation is analyzed. Simulation results show the peak values of acceleration caused by shock wave and reloading are of the same order. The effect of fluid element size on cavitation calculation is investigated by using parallel computers. For simulating cavitation and its effect on structures more accurately, smaller fluid elements are required. This reflects the importance of high-performance computing in the field of underwater explosion research. The research of this thesis is supported by Doctoral Research Foundation of Liaoning Province(NO:20091012).The financial contributions are gratefully acknowledged.