curved-bar rack bypass systems for downstream fish passage
Post on 15-Mar-2022
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Curved-Bar Rack Bypass Systems for
Downstream Fish Passage
FIThydro final Conference
Dr. Claudia Beck
18.03.2021
26.03.2021
2
Mechanical behavioural fish guidance structures
Ur
VpVn
High hydraulic head losses
Asymmetric downstream flow field
HPP operators are hesitant to apply this technology
β = 45° – 90°
α = 10° – 45°
sb = 25 – 100 mm
β
α
sb
Vp > Vn
3
ξR = 14* ~ξR/5 = 2.6* ~ξR/20 = 0.6
Reduction of head loss coefficient:
Example:
• Rack angle α = 30°
• Clear bar spacing sb = 50 mm:
Most CH trash racks: 0.11 < xR < 3.0
(Meusburger 2002)
* Values from Kriewitz (2015)
Louver MBR CBR
Hydraulic head losses
4
α = 30°, β = 45°, sb = 50 mm
2D CFD simulation averaged over 10 s Adapted from Leuch (2019)
α
α
β
β
sb
sb
Effect of bar shape on the flow field
5
Ethohydraulic testsMain objectives:
• Evaluate fish protection and guidance efficiency of CBR-BS
• Link fish behaviour to hydrodynamic cues
Tested fish species:
spirlin, barbel, nase, European eel, brown trout, salmon parr
Main tested hydraulic conditions:
• Mean approach flow velocities Uo = 0.5 m/s, 0.7 m/s
• Bypass entrance velocity ratio Uby,in/Uo = 1.2, 1.4
a = 30°, b = 45°, sb = 50 mm
0.25 m
CBR bypass
fish holding tank
submerged
cameras
Uo
Uby,in
starting
compartment
6
Fish Guidance Efficiency (FGE)
FGE > 85% for spirlin, barbel, nase & salmon parr
FGE < 60% for eels and brown trout
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Effect of flow conditions
→ Higher guidance efficiency for higher approach flow velocitiy (Uo = 0.7 m/s)
→ Higher guidance efficiency for lower bypass inflow velocity ratio (Uby,in /Ua = 1.2)
Uby,in /Uo ↑ ↓ ↑
↑
bypass
passage
rack
passagerefusal
Uo ↑ →
→
↑
3 binary logistic regression models for the response variables
I) bypass passage
II) rack passage
III) refusal
8
Flow fields at the CBR-BS3D CFD simulation averaged over 20 s extracted at 125 mm over the flume bed
Pressure gradient
[Pa/cm]velocity gradient
[m/(sm)]
10
Summary & outlook
• Novel curved bar shape greatly improves the hydraulic performance
o Flow straightening effect symmetric turbine admission
o 4.2 times lower head losses compared to straight bar shapes
• Live-fish tests proved the behavioural barrier effect of
this fish guidance structure type
• CBR-BS have a large potential to protect and guide fish at HPPs and
water intakes with minimal impact on operation & production
• Numerical model allows for optimization of bar shape
and CBR-BS geometry
(Source: Fäh, Wälli AG, VAW; Patent pending EP21155988.5)
Thank you
11
This project has received funding from the European Union's Horizon
2020 research and innovation programme under grant agreement No.
727830, FITHydro.
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