Author(s): Obaidullah Safie, Akihiro Tominaga

Linked Author(s): Akihiro Tominaga

Keywords: Pile-group; Flow structure; Pile arrangement; Permeable spur dike; Riverbank protection;

Abstract: Pile-group dikes as river training structures can be used for velocity control and protection of the banks from severe erosion. Yet no detailed explanation has been found in the literature on how these structures function. In order to study the effects of different pile-groups on the flow, experimental and numerical studies were conducted. Different number of piles per group, which was defined as pile density, was considered. In addition, two types of piles arrangement namely in-line and staggered were applied for each pile density. The results indicate that for all the cases, the flow penetrated to the pile-group and the penetrated flow discharged from the structure with reduced velocity. The magnitude of the velocity downstream of the pile-group is inversely proportional to the pile density, while it is the opposite in the mainstream. By changing the arrangement of the piles from in-line to staggered arrays, significant desirable change occurred in the flow structure. In a lateral section in the downstream of the structure, staggered cases minimized the velocity near the bank and then the velocity was increasing gradually to the mainstream, however, for the in-line arrays it was the opposite. Regarding the turbulence in the channel, the in-line cases generated a strong turbulence region downstream of the structure. Furthermore, a lower pile density in staggered arrays can reduce the velocity as a higher pile density of in-line arrangement. Therefore, staggered arrays had the advantages of using less number of piles. The flow structures around the pile-groups were well simulated by a 2D numerical model.

DOI: https://doi.org/10.3850/38WC092019-0647

Year: 2019