Fig. 4: Inflow characterisation from upstream ADCP transect line.

A Ebb flow transect line (17/04/2022, T5, mean ebb velocity magnitude = 2.8 ms⁻¹) showing absolute streamwise horizontal velocity (|U| ms⁻¹) upstream (100 m or 5D) of the O2. For reference, the downstream location of the O2 is superimposed (hull structure, rotor arms and rotor-swept area in magenta). B Corresponding plot showing the difference in streamwise velocity compared to the velocities experienced in the rotor-swept area of the O2 (|U|-<|U|> _O2 ms⁻¹). The dashed line indicates the inclination of the shear line. C Depth-averaged absolute streamwise velocity with shading indicating ±1 standard deviation. Three sections are indicated (in white, each section is 45 m in cross-stream extent, representing the extremities of the two rotors), the freestream (FS; centred at Y = -100 m), the direct inflow area (O2; centred at Y = 0), as well as the adjacent shear line region (S; centred at Y = 100 m). D Spatially averaged depth profiles of horizontal velocity magnitude (green, shading indicating ±1 standard deviation) of the three sections in (C) with grey lines showing mean profiles from the other sections for reference. The middle panel in (D) also shows the corresponding mean velocity magnitude profile of the turbine-mounted, downward-facing ADCP during the time of the transect line (in magenta). Source data are provided.