Research On Impact And Vibration Characteristic Of Supercavitating High-Speed Bodies With Tail-Slaps

Using supercavitation to enormously reduce the drag on the underwater vehicle is an ideal way to increasing the velocity of the underwater vehicle. A supercavity can minimize the water-contacting surface of the vehicle, thus the friction by the water also would be reduced. Several possible modes of vehicle motion would arise according to the magnitude of velocity of the vehicle and when the velocity is enough large, the vehicle would advance with tail-slapping. The successional impacts as tail-slappings result great difference between the structural dynamics characteristics of a supercacitating vehicle and that of a traditional vehicle.Now there have been many researches about the supercavitating flow, but the researches about the structral dynamics characteristics of the supercavitating vehicle are few. And the researches on structral dynamics characteristics of a supercavitating vehicle with tail-slapping are especially little. But these researches are important to the studies of the structral optimum design and the motion stability analysis for supercavitating vehicle. So, the reserch in this paper has very important theorical and practical values for the prepare and manufacture of the supercavitating weapons.In this paper, the tail-slapping force and the structral dynamics characteristics of the supercavitating vehicle with tail-slapping have been investigated by theoretical analysis and simulation. The main works are as follows: Based on the coupling dynamics theory of elastic beam in large overall rotation and according to the characteristic of the motion of the body, the fundamental frequency and the mode of vibration of a supercavitating projectile with tail-slapping were given and their variations with time were calculated and analysised. Also, the influences of the projectile's slenderness radio, material and rotational velocity on the vibration characteristics were investigated.The calculation of the tail-slapping force is a key and a difficulty for the research of vibration of the projectile with tail-slapping. By the theoretical method and fluid-solid interaction simulations, the impact load of a projectile, which is freely advancing with tail-slappings, was investigated. The variation of the impact load with time and the relation between the load and the structural design parameters of the projectile were given.On the base of the above results of the tail-slapping load, the structral responds of a projectile uhdergoing tail-slapping were simulated. The acceleration responds were analysised respectively in time domain and in frequency domain. The variation and location of the maximum values of the principal stresses were presented. The relation between the structral responds and the parameter of the body were given.In the last chapter of this paper, for the supercavitating vehicle of large demention (the supercavitating torpedo) cruising with uniform speed and undergoing tail-slaps, the structral responds of the body were simulated by FEM (finite element method). The relation between the structral responds and the velocity were obtained.To present, there hasn't been the document on the experimental investigation for the tail-slaps force and the corresponding vibration of a supercavitating veicle. So the results presented in this paper can provide some references for the experimental investigations in the future and benefit the subsequent studies in structral stability analysis and structral optimum design.