Division and flow scale investigation of circulation zone around spur dike

The velocity distribution in the circulation zone around the spur dike is studied by 3D-PDA in the water tank in this paper.According to the distribution characteristic of the velocity and the flux,the general flow field can be divided into three regions in the transverse direction: the reverse-velocity backflow region,the positive-velocity backflow region and the main flow region; and two regions in longitudinal direction: the reverse flow velocity-increasing region and the reverse flow velocity-decreasing region.The longitudinal variation of the each region is also studied,which shows that the width of the negative velocity area and the circulation flow area changes linearly in the longitudinal direction.