THREE-DIMENSIONAL FLOW STRUCTURES AROUND SUBMERGED BOX GROYNE WITH LONGITUDINAL BLOCK

A box groyne is composed of various types of single groyne to satisfy the different river ecological requirements. In order to create an appropriate watery and sedimentary environment for aquatic life in the groyne zone during flooding, the exploration of three-dimensional flow structure around the box groyne under the submerged condition is necessary. The flow velocity around submerged box groynes with a longitudinal block, which is composed by straight and L-shape groyne, are measured by PIV (Particle Image Velocimetry) on the horizontal plane ( x-y ) and vertical plane ( x-z ). The interaction effects between the vertical vortex detached from the crest of the first groyne and the transverse vortex detached from the lateral of the first groyne cause the complex three-dimensional flow characteristics in the box groyne zone. The longitudinal block set in the lateral side of box groyne definitely affects the development of transverse vortex associated with the inflow condition and reduces outflow passages in the lateral interface of box groyne. As to the upper flow, the inlet and outlet of fluid, and also the flow direction are greatly changed by the longitudinal block.