Analysis of convergent and divergent-convergent nozzle of waterjet propulsion by CFD simulation

Waterjet propulsion is a type of propulsion system which is used widely by ship with high-speed operation and sailing in shallow waters. This system is constructed by pump and impeller that impels water passing through the inlet tube. Transport energy is occurred from pump to water, due to rotation of the impeller. Reduction of cross-sectional area at the end of nozzle increases water stream velocity, outcome increasing kinetic energy by a change of momentum because of an acceleration. The work of nozzle can be measured by efficiency and force output which is used to propel ship effectively. These parameters are related to nozzle geometry, as the main factor in this paper, supported by other factors such as pump pressure and stream velocity. The analysis of these parameters is presented by simulation in Ansys Fluent. From the results obtained the efficiency of a convergent nozzle is bigger than combination nozzle, with different values within 8% up to 12%. It suggests this type of nozzle is suitable for saving energy in waterjet propulsion system.