Experimental Hydraulic Investigation of Angled Fish Protection Systems—Comparison of Circular Bars and Cables
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Unit of Hydraulic Engineering, University of Innsbruck, Technikerstraße 13, 6020 Innsbruck, Austria
2
School of Engineering, Institute for Energy Systems, FloWave Ocean Energy Research Facility, The University of Edinburgh, Max Born Crescent, Edinburgh EH9 3BF, UK
*
Authors to whom correspondence should be addressed.
Water 2019, 11(5), 1056; https://doi.org/10.3390/w11051056
Received: 23 April 2019 / Revised: 13 May 2019 / Accepted: 14 May 2019 / Published: 21 May 2019
(This article belongs to the Special Issue Environmental Hydraulics Research)
The requirements for fish protection at hydro power plants have led to a significant decrease of the bar spacing at trash racks as well as the need of an inclined or angled design to improve the guidance effect (fish-friendly trash racks). The flexible fish fence (FFF) is a new developed fish protection and guidance system, created by horizontally arranged steel cables instead of bars. The presented study investigated experimentally the head loss coefficient of an angled horizontal trash rack with circular bars (CBTR) and the FFF with identical cross sections in a flume (scale 1:2). Nine configurations of different bar and cable spacing (blockage ratio) and rack angles were studied for CBTR and FFF considering six different stationary flow conditions. The results demonstrate that head loss coefficient is independent from the studied Bar–Reynolds number range and increases with increasing blockage ratio and angle. At an angle of 30 degrees, a direct comparison between the two different rack options was conducted to investigate the effect of cable vibrations. At the lowest blockage ratio, head loss for both options are in similar very low ranges, while the head loss coefficient of the FFF increases significantly compared to the CBTR with an increase of blockage. Further, the results indicate a moderate overestimation with the predicted head loss by common head loss equations developed for inclined vertical trash racks. Thus, an adaption of the design equation is proposed to improve the estimation of head loss on both rack options.
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Keywords:
fish protection; head loss; intake; hydraulics of renewable energy systems; hydraulic structure design and management; scale model test
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MDPI and ACS Style
Böttcher, H.; Gabl, R.; Aufleger, M. Experimental Hydraulic Investigation of Angled Fish Protection Systems—Comparison of Circular Bars and Cables. Water 2019, 11, 1056.
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