Assessing Scale Effects on a Propeller in Uniform Inflow Condition

Paper in proceeding, 2023

Open water testing for model scales is a universally accepted method to evaluate the thrust, torque, and efficiency of a propeller. Even so, due to the Reynolds number dissimilarity in tests, the development of the boundary layer and the natural transition to turbulence is not the same. This creates discrepancies in the force ratios known as scale effects. To overcome this issue, the standardized ITTC 78 method was developed as an extrapolation procedure to estimate the full scale propeller delivered power and performance. With the development of Computational Fluid Dynamics numerical tools, the scaling issue could be avoided by modeling the geometry in its real sea conditions. This paper aims at studying the scaling effects of a marine propeller in uniform open water condition. The geometry can be described as a moderately skewed 4-bladed controllable pitch propeller mounted on a simplified hub, and the geometrical scaling ratio for the model λ = 27.143. A comparison of the propeller performance across a range of advance ratios J at varying scales will be presented. Results of the numerical simulations will be compared with model scale experimental measurements carried out at Kongsberg’s research facility. The overall aim of this study is to gain a perception of how the scaling effects will influence the performance of this specific propeller.