Vibration Analysis Of Supercavitating Body With Tail-slap And Damping Structural Design

Supercavitation is a new technology which can make a voyage to realize high speed. For its excellent characteristics of drag reduction, the drag reduction of supercavitation can reduce more than 90% body resistance of the vehicle during the underwater navigation, which achieves the revolutionary breakthrough of drag reduction technology in underwater navigation. As the navigation vehicle is covered by supercavitation, the vehicle wet area in fluid medium also gradually decreases,which can reduce the viscous resistance of the fluid medium. Therefore, the dynamic performance of the sailing body is greatly improved by the supercavitation. However,when the high speed vehicle navigates with the speed of up to 300 m/s to the 1000 m/s, the vehicle tail may be continuously impacted or rebounded with cavity wall owing to the initial disturbance and other influences. This phenomenon called tail-slap was observed through the experiments. Because of the special navigation conditions of the supercavitation high-speed vehicle,the tail-slap characteristics appears very special and also owes great research value.In this paper, some analysis softwares,such as MATLAB and LS-DYNA,were used to make and finite element simulation for dynamics and vibration characteristic analysis of supercavitation projectile. During numerical simulation, the tail-slap characteristic of high-speed supercavitation projectile, vibration reduction structure design and the movement stability problems are studied, as follows:Part I: In this part we found out the current situation of the theoretical studies, numerical simulation studies and experimental research of the underwater supercavitating high-speed projectile, and have given a summary of the physical model and the solving method for kinetic differential equations that they are widely used in the underwater projectile kinetic study. Then we establish the dynamic equations for a wide range of rigid body rotation coupled with the elastic vibration of the elastic beam with using the Von Karman large deflection theory and Hamiltonian variational principle, then get the analysis expression of the projectiles vibration frequency and mode shape , carry on the numerical analysis for it in the last.Part II: In this part we analyzed and shown the reason of that the dynamics differential equation for small scale projectile is not suitble for, and the method of dynamic analysis and numerical simulation for the large size projectile that we used in this article. Then we Expounded the characteristics and applicable scope of the different supercavitating model,compared the advantages and disadvantages of them, and chose a suitable cavitation model for the projectile model in this paper to carry on the numerical simulation. Through the analysis of the tail-slap force variation law we can offer the theoretical basis and technical support for the underwater supercavitating high-speed projectile avoiding the tail-slap phenomenon.Part III: According to a type of supercavitating projectile,we established the projectile CAE models, and carried on the numerical simulation and the simulation analysis for these models. Then we analyzed tail-slap dynamic response of the original structure and the structure that has damping device, in the same conditions. Through the analysis of the projectile rigid-displacement and the acceleration of the nodes in the same position of projectile, we can show that the feasibility of damping structure, and provide the theoretical basis and technical support for optimization design of the damping structure in the future research.