Wind and turbulence conditions encountered by vessels and wind-assisted propulsion systems at sea

Time-resolved measurements of the open-ocean marine atmospheric boundary layer (MABL) are essential for characterizing wind conditions encountered by wind-assisted propulsion systems (WAPS). A unique dataset obtained using two upward-facing continuous-wave profiling lidars during four trans-Atlantic crossings of a tanker is presented. On the latter two crossings, suction-type sails were installed on the deck of the vessel. Horizontal wind velocities and apparent wind angles were measured by the first lidar between 10 m and 100 m above deck. The vertical profiles indicate that the apparent wind field is strongly modified by the sails, and that both configurations produce deviations from theoretical boundary-layer power-law profiles. The second lidar continuously measured at 22 m above deck, at a frequency of roughly 1 Hz, to provide time-resolved measurements. Velocity increments exhibit sustained heavy-tailed distributions, presumably due to external intermittency. Two distinct scaling regimes are found: one up to 100 m and a second starting from 10 km. In between, the energy spectrum exhibits a robust 𝑓 − 1 scaling, consistent with the attached-eddy model and indicative of high friction Reynolds numbers ( 𝒪 ⁡ ( 1 ⁢ 0 7 ) ) . The presented measurements, together with representative time series released as a reference dataset, provide unprecedented insight into the real MABL experienced by vessels.