Time-averaged velocity and turbulence intensity at the initial downstream flow from a six-bladed ship propeller

The current study investigated the time-averaged velocity and turbulence intensity at the initial downstream flow from a six-bladed ship propeller. The six-bladed propeller provided the rapid periodical pulses of thrust in one revolution due to the blades leading to a complex downstream jet. The six-bladed propeller is popular as a boat racing propeller, but the presentation of its flow structure was rarely found in the previous studies. In this study, the experiments were carried out in a water tank to measure the time-averaged velocity and turbulence intensity by using a Laser Doppler Anemometry (LDA) system. The jet was produced by rotating the propeller at a constant speed powered by an electric motor. The maximum tangential and radial velocities of the six-bladed propeller were of 76% and 17% of the maximum axial velocity respectively. The study found that the six-bladed propeller has a lower tangential velocity, but a higher radial velocity with its own diffusing mechanism when comparing to the three-bladed propeller. ► Jet from six-blade ship propeller with limited existing documentation is studied. ► Six-blade propeller has a lower tangential velocity, but a higher radial velocity. ► Six-blade propeller has its own diffusing mechanism compared to three-blade propeller. ► Axial, tangential and radial velocities and turbulence intensity are investigated. ► Empirical equation to predict the peak of turbulence intensity is proposed.