抄録
Flow structure around permeable pile-group dikes was investigated experimentally by PIV method. The purpose was to reduce the flow velocity to protect the bank while the influence on the mainstream is small and reduced local scour is expected. The effects of number of piles and arrangement type on the flow structure were studied. The flow structure generated by two pile-group types, namely in-line and staggered arrays was compared. Different number of piles per group which was defined as pile-group density was considered. The results indicate that by changing the arrangement of the piles from in-line to staggered arrays, desirable changes on the flow structure occurred. The following features are particularly noteworthy for staggered array cases. It generated suitable velocity pattern in the downstream of the pile-group. In a lateral section at downstream of the structure it minimized the velocity near the bank and then it was increasing gradually to the mainstream, however, for the in-line arrays it was the opposite. Furthermore, to obtain a certain velocity near the bank, staggered arrays had the advantages of using less number of piles and hence less effect on the mainstream flow. In addition, staggered arrangement significantly reduced the generation of strong turbulence in the channel.
