Investigating the Effects of Air Duct Dimensions on Aeration and Hydrodynamic Characteristics of a Surface-piercing Propeller

In this work, considering a propulsion system of a planing boat, the effects of the air ducts with a square cross-section on the thrust, torque, performance, and ventilation of the surface piercing propeller (SPP) are investigated. The fluid flow is simulated using solving of the Reynolds-averaged Navier–Stokes equations (RANS) by the multi-physics computational fluid dynamics software STAR-CCM+. The simulations are validated by studying its grid independency and comparing the numerical results with the extracted results from the sea trial. Then, by considering the actual arrangement of the duct and SPP, the SPP is examined in the open water test in five cases for both condition of the lack and existence of the aeration. Also, the effects of aeration, the advance coefficient and the immersion ratio on the hydrodynamic characteristics of the SPP are studied. In a constant distance between the air duct and propeller, the results show that by increasing the hydraulic diameter of the air duct, the torque and thrust decrease, and the efficiency remains almost constant. Also, it is numerically demonstrated that the effects of the advance coefficient on the torque and thrust coefficients are different for the models with and without aeration.