Effects of upstream vortex generators on the intake duct performance for a waterjet propulsion system

This paper investigates the effects of vortex generators (VGs) on the flow separation in the intake duct for a waterjet propulsion system. A row of plate VGs is installed on the ship hull bottom upstream before the intake entrance. Flow's RANS equations are solved with the standard SST turbulence model to simulate the flow field inside the intake duct. Results show that the flow separation along the intake ramp wall is restrained leading to improved flow's uniformity before entering the waterjet pump. The VG effects on the intake flow field at various Inlet Velocity Ratio (IVR) conditions are elucidated from the aspects of vortex distribution, flow separation and overall performance. The VG induced extra vortices increases the fluid momentum near the duct ramp wall. The inflow distortions of axial flow velocity and total pressure are reduced before the suction pump. At the designed operation conditions, the flow's hydraulic efficiency flow through the intake duct is increased by 4.3 percent. Compared with the intake duct prototype, the total pressure distortion index on the duct outflow plane is reduced by 37.9 percent. The outflow's uniformity is decreased by 15.8 percent. Miniature shaped VGs have yielded evident improvements on the intake hydraulic performances.