Influence of Finite Tip Clearance on the Tip Flow Characteristics of Ducted Propeller

The influence of finite tip clearances on the tip flow characteristics, as well as pressure distribution on blade surface near the tip and open water performance of ducted propeller 19A/Ka4-55 model is studied in this paper. It is discovered that tip leakage vortex (TLV for short) disappears when clearance size reduces to a certain extent (0.08% of the propeller radius in this model). The decreasing of tip clearance size also leads to increasing efficiency and better cavitation performance. Besides, variation of thrust and torque coefficient with clearance size show stepped shape instead of linear.