Three-dimensional Experiment And Numerical Simulation Study Of The Interaction Between The Vertical Supercavitation Water-exit And Free Surfacc

The emergence of supercavitation technology makes a breakthrough in the drag reduction ofunderwater, by the use of supercavitation technology can be greatly improved the sailing bodies’velocity and range, it is a revolutionary method of drag reduction, and has a very importantapplication value in military, emergency transport ships, offshore personnel emergency. Thesailing bodies with supercavitation’s water-exit is an important part in the study of fluiddynamics, in this process its surrounding environment got a tremendous change in a short time, itinvolves of some theories, such as water-exit, cavity flow, multiphase flow and boundary layer. Inthis paper, I took a method which combined experiment and numerical simulation to have a deepresearch about this complex process of water-exit.By using a set of slender body water-exit experimental device which was designed anddeveloped by our own team, I made an experimental study on different long-radius ratio,different head style, different local structure, different cavitator diameter, different cavitatorlength and different tail structure’s slender bodies, the slender bodies’ water-exit images werecaptured by a high speed camera to realized the water flow of supercavitation visualization,calculated the slender bodys’ velocity, cavitation number, drag coefficient in different conditions.The study found that in a certain range, appropriate increased the long-radius ratio wasadvantageous to the slender body’s underwater drag reduction; the head of slender cone angle issmaller, it is much easier to deflect when underwater high-speed movement, and theballistic stability becomes worse, cone angle is larger and more easily produced super cavitation,better cavitation characteristics, slender body with local arch against the drag reduction ofunderwater movement while local groove had no big effect on the drag reduction characteristics,appropriate increase the cavitator’s diameter and length can improve their underwater dragreduction effect, hemispherical slender has the best drag reduction effect in different tailstructure’s slender body. Also I measured the supercavity’s shape contour and the law of dimension changes in different cavitation numbers, and compared the experimental results withthe pioneer of super cavitation semi-empirical formulas.Due to the limitation of the experimental conditions and measurement errors, on the basis ofthe experimental research, the ANSYS software was adopt to simulated the water-exit processfor the slender body which long-radius ratio was11,15with2D and3D models, then comparedand analyzed the simulation results with the experimental results.