Computational fluid dynamics simulations of water flow on a studded upstream eel pass

Abu B M Ibnu Syihab,Patrick G Verdin,Monica Rivas Casado,Adam T Piper,Rosalind M Wright

doi:10.1002/rra.3837

Abstract

AbstractThe European eel population has undergone a significant decline in recruitment over the last 3–4 decades. Anthropogenic riverine barriers that disrupt the eel's life cycle when migrating upstream are contributory factors in this decline. The development of eel passage facilities is one of many attempts to mitigate this problem. In upstream passes, eels rely on a substrate in the base of the pass to assist their ascent by climbing and/or swimming. This study numerically evaluates, using computational fluid dynamics, the hydrodynamic characteristics of water flow on a studded substrate, under a range of installation angles and water flowrates. To assess and predict the efficiency of the pass, simulated flow field data were used to create pass‐ability maps by comparing simulated velocity data with eel swimming capabilities. An 11° installation angle with a ramp flowrate of 1.12 × 10−3 m3/s per metre width was shown to be likely most suitable for 70 mm long eels, and could be used by eels with sizes up to 150 mm. The numerical study has also shown that under specific water flowrates, installation angles of 30° or more can make the water level fluctuate and splash out of the eel pass, resulting in potential inefficiency in ramp water supply, while posing additional challenges for eels ascending the pass.

Highlights

The European eel (Anguilla anguilla L.) has experienced a significant decline in recruitment since the 1980s (Dekker, 2003)
European eels are spawned in the Sargasso Sea, and the larvae are transported along the Gulf Stream and North-Atlantic Drift during a journey of 10 months to over 2 years to the eastern Atlantic coast (Bonhommeau et al, 2009; Schmidt, 1923)
computational fluid dynamics (CFD) simulation results revealed that the 11 installation angle with a water flowrate of 1.12 Â 10À3 and 1.63 Â 10À3 m3/s creates a water level between 3 and 5 mm, which is suitable for 70 mm eels

Summary

Introduction

The European eel (Anguilla anguilla L.) has experienced a significant decline in recruitment since the 1980s (Dekker, 2003). This phenomenon is possibly caused by a combination of anthropogenic factors that disrupt the lifecycle and reduce survival (Henderson et al, 2012). On reaching the continental shelf, the larvae metamorphose into glass eels, and subsequently elvers, that ascend rivers and will grow for up to 50 years before returning to the Sargasso Sea to spawn. The blockage of eel migration routes in rivers by barriers such as power stations and dams is one of the possible causes of their population decline (van Ginneken & Maes, 2005). The provision of upstream fish passage facilities is a widely used approach to try to mitigate the problem (Feunteun, 2002)

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