Numerical flow simulation of flush type intake duct of waterjet

Waterjet propulsion system is widely used to thrust high speed marine vessels in excess of 30–35 knots by virtue of high propulsive efficiency, good maneuverability, and less vibration. Since, however, approximately 7–9% of the total power is lost in intake duct due to flow separation, nonuniformity, etc., detail understanding of flow phenomena occurring within intake duct is essential to reduce the power loss. The present work solved 3D incompressible RANS equations on multiblocked grid system of the flush type intake duct of waterjet. The numerical results of surface pressure distributions, velocity vectors, and streamlines were compared with experiments and good agreements were obtained for three jet velocity ratios. Strong suction flow through the inlet was shown and the vortex induced by the separation along the corner of the side wall was clearly shown. Flow separation on the lip was also observed. The location of stagnation point on the lip was well predicted, in accordance with PIV measurement.