Hydraulic and dynamic assessment of triangular labyrinth weirs and wier-pool type fishways

Abstract

The hydraulic performance of traditional labyrinth weirs has been extensively studied in the literature. The research outcomes indicated that labyrinth weirs have many hydraulic advantages to pass more flow with a constant water head which reduces the construction cost and improve flood prevention. In this study, a series of laboratory experiments was conducted to test a new weir design based on a classical triangular labyrinth weir. A square pool was added to the vertex of a triangular labyrinth weir in two different directions to form two new designs named as labyrinth weirs with upstream and downstream pools. Detailed velocity and turbulence measurements were conducted using an Acoustic Doppler Velocimetry (ADV) probe to investigate the flow dynamics and turbulence characteristics of the new design in both free and submerged flow conditions. The ability of using a series of the newly design weirs as a fish passage was tested by constructing a series of weirs with different weir spacing. The upstream flow velocities in three directions and the mean and the turbulent kinetic energies (TKE) were measured with the ADV probe. The mean velocity and the turbulent kinetic energy distribution indicated that the maximum range occurred in the corner of the main sidewall of the weir and the pool’s sidewalls. The maximum longitudinal and vertical velocities and TKE for the weir with the upstream pool occurred inside the pool, whereas the maximum lateral velocity located in the vicinity of the main sidewall of the weir. In addition, the lateral velocity in the labyrinth weir with the upstream pool changed to the elevation equal to 70% of the upstream water level.