Numerical Research On Dynamics Of Structures For Supercavitating Vehicles

Under the background of the advance of the undewater vehicle technologies, aseries of structural dynamic problems are found during the development of thesupercavitating vehicle. In this paper, the finite element model was established for thesupercavitating vehicle based on the nonlinear finite element method. Systematical anddeep research was carried out on the structural dynamic characteristics of thesupercavitating vehilce, as well as on the interactions between the cavity and the vehiclebody, revealing the development process and the mechanisms of structural dynamicbuckling and dynamic response for the supercavitating vehicle, providing the theoreticalbasis for the structural design of the supercavitating vehicle.Based on the design theories of the water ramjet motor and the underwater vehicle,the structural configuration of double shells for the propulsive system of thesupercavitating vehicle was proposed and the general structural layout for thesupercavitating vehicle was confirmed. According to the planing motion configurationof the supercavitating vehicle the forces applied on the vehicle body were analyzed,providing the important basis for the numerical research on the structural dynamiccharacteristics of supercavitating vehicles.The plain shell structures of supercavitaiting vehicles were simulated by the shellelements of relative degrees of freedom and isoparameter solid elements, and thenonlinear finite element formulation based on the Updated Lagrange framework wasderived. The double shells structures of supercavitating vehicles were developed withthe equivalent monolayer model, the double layer model and the double liquid-filledmodel. Based on the gap element contact theory the finite element model of connectingstiffness was developed for the axial and radial connection configurations. The finiteelement model for the supercavitating vehicle was verifed by computing cases, and theabove research set the theoretical and method basis for the simulation on structuraldynamics of the supercaviting vehicle.The theoretical and numerical models of the hydrodynamic loads during theplaning of the supecavitating vehicle on the cavity were developed according to thetheory of water entry impact of the structure and the ALE finite element method. Theeffects of the velocity and the disturbance angular velocity of the supercavitatingvehicle on the hydrodynamic loads were analyzed and the theoretical model of thehydrodynamic loads for the structural dynamic response of supercavitating vehicles wasobtained by the comparison of the numerical results.Based on the finite element model of Updated Lagrange formulation, the numericalresearch on the structural dynamic buckling of supercavitating vehicles was performedusing the theory of structural buckling and nonlinear finite elemet method. The effects of velocity of the vehilce and the frequency of the wetted surface on the dynamicinstable regions were analyzed, and the thickness of the shell structures, the physicaldimensions of the double shells and the stiffeners configurations were investigated forthe mechanisms of structual dynamic stability, and the effects of the axial and radialconnection configurations on the structural dynamics was analyzed, providing technicalsupport for the development of numerical dynamics of structures of supercavitatingvehicles.The research on the structural dynamic response of supercavitating vehicles wascarried out using of the co-rotational formulation and non-conservative system stabilitytheory. The effect of velocity on the dynamic response was analyzed, and the thicknessof the shell structures, the physical dimensions of the double shells and the stiffenersconfigurations were investigated for the mechanisms of structual dynamic response. Theobained numerical results provide the theorical basis for the design of the structures forsupercavitating vehicles.The research achievements in this thesis will surely promote the develoment ofsupercavitating vehicles, as well as providing support for the advancement of thesimulation techniques for the structures of supercavitating vehicles. The research will beof great theoretical value as well as engineering practice meaning for the futuresupercavitatng vehicle design.