Hydrodynamics of Atlantic salmon culture tank: Effect of inlet nozzle angle on the velocity field

Authors: GORLE, JAGAN - Nofima; TERJESEN, BENDIK FYHN - Nofima; SUMMERFELT, STEVEN - Freshwater Institute

Submitted to: Computers and Electronics in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2019
Publication Date: 3/1/2019
Citation: Gorle, J., Terjesen, B., Summerfelt, S. 2019. Hydrodynamics of Atlantic salmon culture tank: Effect of inlet nozzle angle on the velocity field. Computers and Electronics in Agriculture. 158:79-91. https://doi.org/10.1016/j.compag.2019.01.046.
DOI: https://doi.org/10.1016/j.compag.2019.01.046

Interpretive Summary: As the aquaculture industry adopts larger rearing tanks for Atlantic salmon production, the design and construction of these tanks must be optimized to maintain effective and efficient fish production. In particular, the hydrodynamic profile (how the water flows through these tanks) is important to maintain optimal swimming speed and maximize water mixing and flushing of solid wastes from the tanks. In this study we used full-scale computational fluid dynamics (CFD) modeling to compare the hydrodynamic profile of existing tank designs with two new designs. This study identified relatively minor construction changes, as assessed by CFD modeling, that can result in significant and beneficial changes to the hydrodynamic profile of large salmon culture tanks.

Technical Abstract: The aquaculture industry is increasingly interested in using larger rearing tanks of near 1000m3 to achieve production and economic benefits. Higher Reynolds number due to that order of tank size makes the flow fully turbulent. This paper presents a full-scale computational fluid dynamics (CFD) model of an existing culture tank of 788m3 size was developed, based on time-dependent incompressible unsteady Reynolds averaged Navier-Stokes (URANS) formulation with the realizable k-e viscous model. The tank has two inlet pipes, placed closed to side walls of the tank. Each pipe has 11 inlet nozzles, which introduce the flow into the tank parallel to the walls. This base case was validated against the experimental velocity measurements using Acoustic Doppler Velocimetry (ADV) at predefined locations across the central vertical plane of the tank. Turbulence characteristics and hence the hydrodynamic performance of the tank are influenced by inflow characteristics. To conclude this, two redesigns were developed and contrasted with the base design for various flow parameters from the viewpoint of the tank's performance. Redesign 1 has the nozzles turned towards the centre by 42°, while Redesign 2 has bottom 5 nozzles directing the flow towards the centre with the rest injecting the flow parallel to the wall. Distribution of turbulence parameters and vortices reveal that the inflow with a radial component improves the mixing and flow uniformity characteristics of the tank. The present study has shown that relatively minor construction changes aided by CFD can result in major changes in the hydrodynamic properties of large culture tanks for Atlantic salmon.