Shows outwards movement of flow field around a bend.

What is it about?

Advection due to secondary circulation deforms the vertical profile of the primary flow which would normally be logarithmic in shape. A consequence of this is that the vertical shear is reduced which in turn reduces the driving force of secondary flow. Moving vessel Acoustic Doppler Current Profiler (ADCP) measurements from a curved tidal channel of the Otago Harbour show the radially outward movement of the cross-channel velocity maxima as flow progresses around the bend. This outward movement is due to advection of momentum by secondary circulation and is contrasted between ebb and flood tide. This radially outwards movement is approximately 40 m or 10% of the channel width. These measurements are of a much larger flow regime, ≈4000m3s−1, than previous works so this increase in scale makes these observations robust to the effects of measurement noise.

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Why is it important?

Adds to body of knowledge of curved open channel flow. Important for engineering applications such as river channel migration, bank erosion and flood protection.