Numerical Simulation of the External Flow-Field of Pulsed Anti-riots Water-Cannon

The 2-D development process of water cannon is numerically investigated and visualized by a new type of integrated simulation technique. CFD (Computational Fluid Dynamics) analyze focused on the distribution of pressure, velocity and turbulence kinematic energy. Utilizing the governing equations for high-speed flow based on the LES-VOF model, a parallel computation is performed to clarify the detailed process of a cylindrical nozzle flow and to acquire data, which is difficult to confirm by experiment, such as velocity distribution, turbulence kinematic energy in some concrete regions and so on. According to the present analysis, the shape of the external flow-field of the water cannon like a mushroom, then turn to a hemisphere water-bullet, and finally like a camber. The velocity of gas-phase increases to near 500m/s rapidly in the near-field. The pressure decreases to normal atmosphere within 15ms. The maximum of turbulence kinematic energy move to both sides from center with the development of time, and this phenomenon is considered as the main reason conduce to the breakup of liquid-phase.