Author(s): Eric Lillberg; Mikaela Larsson; David Florian Vetsch; Kamal Prasad Pandey; Bjorn Winther Solemslie; Ismail Albayrak; Armin Peter; Torbjorn Forseth; Ole Gunnar Dahlhaug; Robert M. Boes; Ana T. Silva

Linked Author(s): Ismail Albayrak, Ole Gunnar Dahlhaug

Keywords: CFD; DES; OpenFOAM; Downstream fish migration; Fish passage; Behavioural guidance structure

Abstract: In the scope of the FishPath project, the behavioral response of Atlantic salmon smolts (Salmo salar) and European eels (Anguilla Anguilla) to different types of vortex generating obstacles is investigated. Tests of three different vortex generating obstacles, together with observations of resulting fish behavior, were performed in two different size laboratory flumes at ETH Zurich. In the small-scale flume tests, only two obstacles were present, and the turbulent flow field was measured using ADV. In the medium size flume tests, several more obstacles were used to form a continuous Eddy-based fish Guidance Systems (EGS). In an additional small-scale test performed in a flume at NTNU Trondheim, similar obstacles were also used together with PIV measurements to capture the details of wake formation close to the obstacle. The two small flume tests provide the hydraulic data used for verification and validation of a computational fluid dynamics (CFD) model, which is in turn used to evaluate the vorticity created by the different types of EGSs developed within the FishPath project. The CFD model is developed using the open-source computational physics tool OpenFOAM. The Navier-Stokes equations for incompressible, viscous flow are solved using a finite volume framework together with an improved delayed detached eddy (IDDES) turbulence model for closure. The turbulent flow fields and eddy structures for several EGS configurations and different approach flow velocities are evaluated. For some EGS configurations, the free surface is also included by a volume of fluid (VOF) approach. The simulated mean and time dependent flow quantities are compared to measurements and show very good agreement for cases both with and without the free surface.

DOI: https://doi.org/10.64697/iahr.proc.ise2026.abs.216

Year: 2026