Author(s): W. M. L. K. Abeyratne; P. S. Weerasinghe; S. B. Weerakoon
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Keywords: Weir and pool fishway; Optimize; Velocity; Turbulent kinetic energy; Energy dissipation rate
Abstract: Anthropogenic obstacles across the water bodies which slow down and obstruct fish migration causes a high fish population shrinkage in natural water bodies. Appropriately designed fishways with suitable hydraulic conditions, contribute to mitigate these adverse effects by bypassing these anthropogenic obstacles. In the present study, flow in a weir and pool fishway with orifices was investigated by experimental and numerical modelling approaches to optimize the fishway design. The 3-D model was calibrated and verified using measurements obtained by laboratory experiments. The numerical model was then applied to compute the variation of water depth, velocity, turbulent kinetic energy and energy dissipation rate distributions for four fishway slopes ranging from 7% to 13% and for seven baffle arrangements. Experiments were conducted for the slopes, 11% and 13% by varying the downstream water depth to investigate the effect of tail water condition on fishway flow. The mild slope of the fishway geometry was shown to result in a fishway hydraulically suitable for fish passage, overcoming the fish fatigue. The maximum velocities in the fishway can be reduced by controlling the depth at the downstream of the fishways to further increase the fishway slope to economize the design while maintaining a suitable velocity pattern. Moreover, the study compares the hydrodynamics and assess the hydraulic suitability of eight baffle arrangements of weir and pool fishways. For this purpose, a computational fluid dynamics (CFD) model was used to examine the flow field characteristics and turbulence structure of flow maintaining constant discharge, slope, pool volume and size of orifices and weir.
Year: 2020