Annular cavitator with water injection is one of the key parts of the long-range supercavitating vehiclepowered by water ramjet. In this paper, hydrodynamic properties of annular cavitator are studiednumerically. The standard k ~ ε turbulence model is coupled with the Reynolds Averaged Navier-Stokes(RANS) equations to model the natural supercavitation process. The multiphase flow is considered asa mixture of varying density and modeled by the mass exchange equations. To fully understand this process,numerical simulations were performed for different annular cavitators. Computational Fluid Dynamics(CFD) results, including the pressure distribution and forces acting on the cavitator surface, mass flowand pressure loss of water injection, various supercavity sizes, were obtained and analyzed. The pressuredistribution on the cavitator surface was significantly changed which resulted in 4 ~ 6% increase of thetotal drag of the vehicle. The results show that the mass flow and velocity of the injection water is mainlydependent on the tube size, while the total pressure loss of the water injection is mostly related to the outletpressure. Supercavity generated by annular cavitator is smaller than that of the discal one. Based on thecorrelation analysis of the supercavity size and other factors, it could be concluded that the contraction ofthe cavity size is mainly caused by the diffluent mass flow of the water injection.
