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In quest of better propulsive efficiency for the gas- pressured waterjetrocket , first we must establish genuine propulsive theoretical fluid dynamics analysis methods. In this paper , we generally refer Lagrangian Reynolds transport equation and propulsion power equations developed by Hsing-Juin Lee to analyze the propulsion theory of gas-pressurized waterjet rocket.The traditional scheme of high speed exit jet flow to increase waterjet thrustwill usually involve large kinetic energy loss. We propose to diverge thewaterjet nozzle to increase the outlet pressure. In that sense , we use theturbulent model to calculate the velocity and pressure fields of waterjet nozzle flow. The velocity flow field of divergent nozzle often blends with secondary back flows to form velocity distribution like a maxican chapeau.Therefore , an overly diverged nozzle cannot ensure upswing for the thrustof a waterjet rocket rocket. While carrying out the numerical analysis of thedivergent nozzle and convergent nozzle with 6.5 angle shows better performance. Meanwhile , we may also change the inlet flow or rocket velocities to upgrade its propulsion efficiency. In practical design of awaterjet rocket , we may try to match the rocket system parameters with the fluid pressure , nozzle size , curvature , and etc., in order to improve its propulsive efficiency.
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