Abstract
Velocity measurements were carried out in a river of straight reach with a series of groynes on one side of the main channel. An Acoustic Doppler Current Profiler (ADCP) mounted on a small boat was used. The measurements were performed under three depth conditions including two submerged cases. Flow patterns induced in groyne fields, exchange processes between the main channel and the groyne field, and local flow peculiar around groynes, are of interests.
2-D large circulation flow is dominant in the non-submerged condition, whereas a vertical vortex is formed just behind a groyne in the shallow submerged case, then these circulating patterns in a groyne field are totally washed away in the deep submerged case. The maximum velocity filament in the main channel appears at different positions as the water depth changes owing to the groynes' effect. A slow water body leaving a groyne and showing a boil-like motion is clearly detected.
