Experimental investigation of aerodynamic loading on rotor sails at full dynamic similarity*

A major challenge in the research of rotor sails for wind-assisted propulsion on maritime vessels is the limited understanding of aerodynamic loading coefficients scaling with operational parameters. This knowledge gap stems from the lack of experimental and numerical results at conditions close to full-scale operational envelopes of rotor sails. The present study experimentally investigates the effect of Reynolds number (Re_D), velocity ratio (λ), aspect ratio (AR), and tip effects on the lift and drag coefficient of a finite-span rotating cylinder. Experiments are conducted in the High Reynolds number Test Facility at Princeton University, where conditions close to full-scale and are achieved by varying flow velocity and density. Loads and power are measured for Re_D ∈ [0.5,4.5] x 106 and λ ∈ [0,5] for various AR and endplate configurations. The results provide novel insight into scaling laws of loading and power coefficients over an unprecedented range of Re_D and λ, providing a dataset that spans conditions achievable in the laboratory to full-scale rotor sail operation. This work lays a foundation in investigating rotor sails for wind-assisted ship propulsion systems aimed at reducing transport emissions.