Experimental and numerical investigation of hydrodynamic performance of a new surface piercing propeller family

Abstract

Today, passenger and racing boats increasingly utilize surface-piercing propellers. This type of propeller operates in two distinct phases of water and air simultaneously. As a result, this propeller type has additional characteristics that must be investigated separately from conventional propellers. A new family of surface piercing propellers was investigated using experimental and numerical methods. The family consisted of five propeller models with varying geometric features operating at an immersion ratio of 0.7. Experiments were conducted in the Sharif University of Technology's hydrodynamic group's cavitation tunnel. Additionally, using Star-CCM + software, the numerical simulation was performed using the RANS method for implicit unsteady flow with a sliding mesh technique in free surface conditions. The results indicate that by increasing the pitch ratio from 1.074 to 1.61, the critical advance coefficient value, which is in the range of 0.4–0.6, moves to 0.8–1 interval. Also, the efficiency enhances by 14% while raising the pitch ratio. The amplitude of force and moment fluctuation components increases at higher than 0.5 values of the advance coefficient by increasing pitch ratios. The expanded area grows proportional to an increased number of blades and as a result, the thrust and torque coefficients increase, but the efficiency does not improve significantly. Furthermore, the fluctuation amplitude of forces and moments applied to the key blade increases up to the critical advance coefficient in all models and then decreases for above critical values.