Numerical Simulation Of Supercavitation Around Transonic And Supersonic Projectiles

Cavitation is a special phenomenon of flowing liquid. When pressure of the liquid falls below its saturation pressure, vaporization of liquid occurs. It can reduce the drag of supercavitated projectile obviously. Now supercavitating projectile has become a hot research topic in the field of fluid mechanics.Compared with flow around conventional underwater vehicles, flow around underwater transonic and supersonic supercavitating projectile has many different properties. Compressibility of water and consequent thermal effect must be considered because of super-high speed. However, general computational fluid dynamics code cannot put directly these simulation works into execution. To simulate these complex phenomena needs secondary development on CFD code. So far few paper on this subject has been published in the world.First in this thesis, the progress of cavitation research in the world were systematically reviewed and summarized. And then the flow around underwater transonic and supersonic supercavitating projectiles were simulated with different methods, based on a single-fluid with variable density, what is called Mixture model, and state equation of compressible water (i.e. Tait equation), and redefinitions of sound speed in water and saturate vaporization pressure of water by user defined functions in general CFD code Fluent.The main progresses are indicated in the following aspects: (1) Multiphase flows around transonic and supersonic supercavitating projectile, in which liquid phase is incompressible, were computed and a comprehensive analysis and comparison were made. (2) Multiphase flows around supercavitating projectile, in which liquid phase is compressible, were computed by adjusting density of liquid phase and then a comprehensive analysis and comparison between the two kinds of multiphase flows were made. Some experiences during computation were summarized. (3) The single-phase flow of incompressible water and compressible water were computed, including temperature field. The results show that the compressibility of water can increase drag of supercavitating projectile and generate a lot of heat, and the computational thermal phenomenon is in accord with some experimental observation.