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Article

Numerical Study of Three-Dimensional Surface Jets Emerging from a Fishway Entrance Slot

Federal Waterways Engineering and Research Institute (BAW), 76187 Karlsruhe, Germany
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Author to whom correspondence should be addressed.
Academic Editor: Ismail Albayrak
Water 2021, 13(8), 1079; https://doi.org/10.3390/w13081079
Received: 16 February 2021 / Revised: 8 April 2021 / Accepted: 9 April 2021 / Published: 14 April 2021
(This article belongs to the Special Issue Fish Passage at Hydropower Dams)
The efficiency of a fishway is determined by the ability of immigrating fish to follow its attraction flow (i.e., its jet) to locate and enter the fishway entrance. The hydraulic characteristics of fishway entrance jets can be simplified using findings from widely investigated surface jets produced by shaped nozzles. However, the effect of the different boundary conditions of fishway entrance jets (characterized by vertical entrance slots) compared to nozzle jets must be considered. We investigate the downstream propagation of attraction jets from the vertical slot of a fishway entrance into a quiescent tailrace, considering the following boundary conditions not considered for nozzle jets: (1) slot geometry, (2) turbulence characteristics of the approach flow to the slot, and (3) presence of a lateral wall downstream of the slot. We quantify the effect of these boundary conditions using three-dimensional hydrodynamic-numeric flow simulations with DES and RANS turbulence models and a volume-of-fluid method (VoF) to simulate the free water surface. In addition, we compare jet propagation with existing analytical methods for describing jet propagations from nozzles. We show that a turbulent and inhomogeneous approach flow towards a vertical slot reduces the propagation length of the slot jet in the tailrace due to increased lateral spreading compared to that of a jet produced by a shaped nozzle. An additional lateral wall in the tailrace reduces lateral spreading and significantly increases the propagation length. For highly turbulent flows at fishway entrances, the RANS model tends to overestimate the jet propagation compared to the transient DES model. View Full-Text
Keywords: turbulent rectangular jet; vertical slot; attraction flow; lateral wall; DES; RANS turbulent rectangular jet; vertical slot; attraction flow; lateral wall; DES; RANS
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MDPI and ACS Style

Mahl, L.; Heneka, P.; Henning, M.; Weichert, R.B. Numerical Study of Three-Dimensional Surface Jets Emerging from a Fishway Entrance Slot. Water 2021, 13, 1079. https://doi.org/10.3390/w13081079

AMA Style

Mahl L, Heneka P, Henning M, Weichert RB. Numerical Study of Three-Dimensional Surface Jets Emerging from a Fishway Entrance Slot. Water. 2021; 13(8):1079. https://doi.org/10.3390/w13081079

Chicago/Turabian Style

Mahl, Lena; Heneka, Patrick; Henning, Martin; Weichert, Roman B. 2021. "Numerical Study of Three-Dimensional Surface Jets Emerging from a Fishway Entrance Slot" Water 13, no. 8: 1079. https://doi.org/10.3390/w13081079

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