Author(s): Fawaz Alzabari; Pablo Ouro; Catherine Wilson

Linked Author(s): Catherine A. M. E. Wilson

Keywords: Leaky barrier; Natural flood management; Large Eddy Simulation (LES); Hydrodynamics

Abstract: Large-eddy simulations (LES) were used to study turbulent flow dynamics downstream of linear leaky barriers and the impact of barrier length on wake hydrodynamics. Simulations were conducted on three-row configurations with different numbers of dowels: 6,9, 12,15,18, and 24, corresponding to varying longitudinal lengths (Ls) from 0.05 m to 0.2 m. LES-predicted water surface profile and velocity distributions agreed well with experimental data. Analysis of streamwise velocity distributions revealed important flow characteristics. A high momentum region forms beneath the structure, creating a fast wall jet with decreasing streamwise velocities further from the barrier. Decay in maximum wall jet velocity varies across cases, with the highest decay found in the case with 12 dowels (40.79%) and the lowest in the case with 6 dowels (19.57%). Inter-log gaps generate weak, small offset jets that merge when the upper offset jet deflects towards the lower one. High vertical velocity occurs in the lower wake due to fluid acceleration through the barrier-bottom wall gap. For barriers with Ls ≥ 0.1 m, the high vertical velocity region splits into two smaller areas. The newly-formed region is where separated flow converges to the barrier's bottom surface, approximately 3 diameters from separation. The main flow veers towards the bottom wake, with the shortest barrier displaying a larger recirculation zone near the free surface compared to longer barriers, which have smaller recirculation zones due to reattachment flow occurring closer to the barrier. Mean turbulent kinetic energy and vertical Reynolds shear stress contour plots for cases with 15,18, and 24 dowels are relatively similar, suggesting that increasing the barrier length beyond Ls = 0.125 m is unlikely to alter the wake dynamics. These results offer valuable insights into hydraulic effects of different leaky barrier configurations and inform practical applications.

DOI: https://doi.org/10.3850/978-90-833476-1-5_iahr40wc-p0154-cd

Year: 2023