Multiphase Flows

Fish Injury and Mortality During Passage Through Pumping Stations

[+] Author and Article Information
B. P. M. van Esch

Department of Mechanical Engineering,  Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands

J. Fluids Eng 134(7), 071302 (Jun 21, 2012) (9 pages) doi:10.1115/1.4006808 History: Received October 12, 2011; Revised May 04, 2012; Published June 21, 2012; Online June 21, 2012

An unwanted side effect of pumping stations is that fish suffer from injury and mortality when passing through the pumps and that fish migration is hampered. In recent years, the development of so-called fish-friendly pumping stations has received increasing attention from European governmental institutions and pump manufacturers. In the Netherlands, many field studies have been conducted over the last decade to assess the chances of survival for fish passing through pumps. A clear correlation between observed injury or mortality and, for example, flow rate, shaft speed, or pump type could not be established. This paper presents a new analysis of these field studies. It uses American studies on the biological criteria for fish injury, the most important of which are pressure changes, shear forces, and mechanical injury. A blade strike model is adapted to fish passing through centrifugal pumps of radial, mixed-flow, and axial type. It reveals the relation between fish injury and the type of pump, its size, shaft speed, and pressure head. The results correlate fairly well with experiments. The flow through a typical mixed-flow pump is calculated using computational fluid dynamics (CFD). The results show that pressure fluctuations and shear forces are not likely to add much to fish mortality. Guidelines for the design and selection of fish-friendly pumps are given with the introduction of two new dimensionless numbers: the blade strike probability factor and the blade strike velocity factor. It shows that fish-friendliness of pumps decreases with increasing specific speed value.

Copyright © 2012 by American Society of Mechanical Engineers
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Figure 1

Combined injury and mortality rates in centrifugal pumps of different pumping stations in The Netherlands, showing dependency on shaft speed, flow rate, and head [3]. Values are averages for eel and other species.

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Figure 2

Injury and mortality rates of eel and other fish species, for pumps of different type [3]

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Figure 3

Fish mortality following exposure to brief and rapid pressure drop [12,14]. Suggested thresholds for minimum pressure ratio are indicated [12].

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Figure 4

Pressure reduction in a mixed-flow pump with pa the reference pressure in the suction pipe

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Figure 5

Vorticity magnitude in a mixed-flow pump

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Figure 6

Schematic of a fish entering an axial pump in alignment with the flow

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Figure 7

Graphical representation of data in Table 2

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Figure 8

Comparison of predicted mortality Pm and observed rate of injury and mortality. The dashed line represents full agreement between measured and predicted mortality.

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Figure 9

Blade strike probability factor fP and blade strike velocity factor K1 as a function of specific speed. Guidelines for D1 /D2 , δ, and Km 1 according to Stepanoff [31].

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Figure 10

Blade strike velocity v1 as a function of manometric head, for pumps of different specific speed, operating in a broad working range




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