Author(s): Obaidullah Safie; Akihiro Tominaga

Linked Author(s): Obaidullah Safie, Akihiro Tominaga

Keywords: Flow resistance; Momentum; Velocity reduction; Pile-group; Pile arrangement

Abstract: A pile-group layout parameters have significant effects on the flow around the structure. In this study, flow resistance and velocity reduction were studied around various pile-groups. The number of piles was changed in longitudinal direction of a pile-group, while it was kept constant in lateral direction. Additionally, two arrangement of piles, namely in-line and staggered, were considered for each case. The main purpose was identifying a relation between the velocity reduction rate behind the pile-group and the drag force exerted by the structure. Flow was recorded using the particle image velocimetry, PIV, method. An increase of the number of piles resulted in a decrease of the velocity behind both the in-line and staggered pile-groups. Flow resistance was expressed in terms of the pile-group drag force using the momentum equation. The drag force exerted by the pile-group controlled the velocity reduction behind the structure. The velocity in the pile-group region decreased almost linearly with an increase of the drag force. From the velocity reduction trend in the in-line and staggered pile-arrangements, it was revealed that the velocity reduction caused by a pile-group was determined by the drag force of the pile-group in spite of the different pile arrangements. Additionally, the flow deceleration pattern shows significant difference between the in-line and staggered arrangements. A gradual flow deceleration pattern was reached by increasing the number of piles in the staggered cases. However, it was non-smooth in all the in-line cases.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022810

Year: 2022