Author(s): Martin Zaschke; Melissa Bohm; Lena Mahl; Roman Weichert
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Keywords: Vertical slot fishway; Turbulence; Vortex stretching
Abstract: The suitability of a fishway for upstream migration depends, among other criteria, on the turbulence conditions. Currently, a few recommendations defining maximum acceptable levels of turbulent kinetic energy and its production rate are available in some technical guidelines and scientific papers. In general, however, the question of turbulence impact on fish swimming is a subject of ongoing research (see, e. g. Lacey et al., 2012) and many aspects of fish-flow interactions are not fully understood yet. The focus of this contribution is on the peculiarities of turbulent fluctuations in and close to the slot of vertical slot fishways. Turbulent kinetic energy is usually less in this area than in the high-shear region further downstream where the jet issues into the pool. However, due to the fact that mean flow velocities are near their maximum in the slot and migrating fish must pass this bottleneck, particular attention should be paid to superimposed fluctuations that might locally impede or facilitate fish passage. In this contribution, a combined evaluation of turbulence data recorded in a real fishway, numerical simulation output and theoretical considerations with emphasis on the near-field of the slot are presented.
Year: 2024