Experimental And Simulation Study On Supercavitation Of Small Scale Underwater Moving Body

Cavitation refers to the vaporization phenomenon when the fluid pressure near the body is lower than the saturated vapor pressure in this state when moving at high speed,or the phenomenon that the surface of the body is covered with a layer of non-condensable gas to form a low-density void containing vapor or gas by artificial ventilation device.When the void can completely encapsulate the body,a Supervoid is formed.Because supercavitation can make the body completely encapsulated by gas,only the small surface of the head and tail directly contacts with the fluid,which greatly reduces the viscous resistance of the body and reduces its resistance by more than 90% compared with the full wet state,so the speed of the body will be significantly increased.At present,supercavitation drag reduction technology is one of the most effective methods for underwater drag reduction.In this paper,the supercavitation phenomenon of small-scale underwater vehicle is studied by means of experiment and numerical simulation.Firstly,the projectile experimental device was designed and the supercavitation experiment was carried out.The advantages and disadvantages of existing projectile experimental devices are analyzed and summarized.The design scheme of supercavitation projectile experimental device is determined,and the projectile experimental device is built.Through projectile experiment,the natural supercavitation formation process and its development rule are captured by high-speed camera.The experimental results are compared with the numerical simulation results,and the correctness of the numerical model and simulation method is verified.Subsequently,the cavitation phenomena of a fixed-shape cavitation generator,including disc,hemisphere and cone,are studied by means of numerical simulation.Based on Schnerr-Sauer natural cavitation model,the supercavitation morphology and drag characteristics of different head-type vehicles are simulated and studied.The relationship between the size parameters and drag characteristics of supercavitation and the diameter of disc,hemispherical head-type vehicle or the conical angle of conical head-type vehicle is obtained.The advantages and disadvantages of cavitation and drag characteristics of different head-type vehicle are compared and analyzed,and the navigation characteristics of different head-type vehicle are also analyzed.A comparative study on the development of free-closing and non-free-closing supercavitation is carried out.It is found that the overall size of free-closing supercavitation is basically the same.Finally,the shape-adjustable cavitator is numerically simulated by using dynamic mesh technology.The advantages and disadvantages of traditional adjustable cavitator are analyzed in terms of cavitation characteristics and drag characteristics.A new type of adjustable cavitator is designed on the basis of disc and conical head Supercavitation Flow research,and numerical simulation is carried out.It is found that the cavitation characteristics of the new type of adjustable cavitator are similar,but more important.Good resistance characteristics.