Investigation on the flow characteristics near the duct of a pump-jet propulsion under different advance coefficient conditions.

The flow near the duct is very important for the efficiency and stable operation of a pump-jet propulsion. To study the flow near the outer surface and outlet of a duct, the larger-eddy simulation (LES) method is used to analyze the flow characteristics under different operating conditions. C v on different lines in the swirling-jet flow obtained by the LES method fits well with that of the laser Doppler velocimeter experiment. Based on the reliable results of numerical simulation, it was found that lower inflow velocity delays the generation of separation vortex on the duct's outer surface. When the developing separation vortex interacts with the swirling-jet flow, the strong interaction may destroy the structure of the tip leakage vortex and has a huge influence on the swirling-jet flow with the increasing advance coefficient. As a result, the stronger interaction makes the downstream swirling-jet flow even more complicated. In addition, the strongest intensity of the hub vortex occurs when the advance coefficient is 1.4. u i ′ u j ′ ‾ is very important for the reallocation of the time-average fluctuation kinetic energy. Therefore, it is selected for further flow analysis. Compared with others terms, u z ′ u z ′ ‾ has larger magnitude and is consistent with the distribution of C k. • The developing flow near the duct of an axial water-jet pump is studied based on LES method under three typical conditions. • With the increasing velocity of inflow, the stronger interaction of separation vortex and swirling-jet flow makes the swirling-jet flow more complicated and uneven. • Compared with others terms, u z ′ u z ′ ‾ has a dominant role for the swirling-jet flow. [ABSTRACT FROM AUTHOR]