Propeller characteristics in oblique flow at model scale and full scale

Paper in proceeding, 2024

The prediction of the performance of marine propellers typically relies on data obtained at model-scale under a uniform flow condition. This contrasts heavily with the actual operation of the propeller, which besides operating in the wake of the ship, can also encounter oblique flow due to shaft inclination, waves, maneuvering or a leeway angle experienced by the ship in the case of wind propulsion. This paper investigates numerically the performance of a marine propeller at both model-scale and full-scale when the propeller experiences oblique flow. The results obtained show that when operating under an oblique flow, the mean thrust and torque coefficients of the propeller are slightly higher than those obtained for a condition with the same incoming flow velocity magnitude and where the flow is normal to the propeller plane, with the increase of the thrust being larger. The effect becomes stronger as the propeller is unloaded, which can be particularly important for scenarios corresponding to wind propulsion. Throughout one revolution of the propeller, the blades experience a strong variation in the hydrodynamic loads, which grows with the drift angle and depends on the loading of the propeller. In spite of this variation, the propeller as a unit exhibits a nearly constant thrust and torque. The same trends were observed at model-scale and full-scale, although the effects appear to be weaker at full-scale.