Qualifying the design of a floating closedcontainment fish farm using computational fluid dynamics

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

Submitted to: Biosystems Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/30/2018
Publication Date: 11/1/2018
Citation: Gorle, J., Terjesen, B., Holan, A., Berge, A., Summerfelt, S. 2018. Qualifying the design of a floating closedcontainment fish farm using computational fluid dynamics. Biosystems Engineering. 175:63-81. https://doi.org/10.1016/j.biosystemseng.2018.08.012.
DOI: https://doi.org/10.1016/j.biosystemseng.2018.08.012

Interpretive Summary: With current interest in constructing sea-based floating closed- and semi-closed salmon rearing aquaculture systems, the construction and design of the fish culture vessels must be optimized for hydrodynamic properties (how the water flows through these vessels) that affect fish swimming speed, water mixing, and flushing of solid wastes from the vessels. This study used computational assessments of various water flow characteristics for a standard one-column versus a proposed two-column water inlet configuration in vessels of different sizes. Considerable influence of the inlet configuration on particle motion was observed, and it was determined that the proposed two-column water inlet configuration was more efficient at flushing of solid wastes from the vessels.

Technical Abstract: In order to overcome the environmental consequences of traditional net pens in producing Atlantic salmon, closed containment aquaculture systems are being developed, where the culture volume is separated from the ambient environment by an impermeable wall. However, several challenges in terms of construction and hydrodynamic properties must be solved before such systems can be used on a large scale. A study was thus performed on the design of a floating closed-containment fish farm in sea. This paper presents the design and flow analysis of two versions of the globe; first is the pilot design of a 74 m3 globe, and the second is the design of a 3500 m3 globe for post-smolts of Atlantic salmon. The results of turbulence model of the pilot globe were validated against the velocity measurements using acoustic Doppler velocimetry. Computational assessment of various flow characteristics includes the velocity and vorticity fields. The streamline pattern confirmed the secondary vortices, creating the tea-cup hydrodynamics. Coherent vortices, identified by means of Q-criterion, show the presence of vortex column in the globe. Two inlet configurations were tested on the post-smolt globe for improved performance. Design 1 has the standard one-column nozzle configuration, and the Design 2 has two-column nozzles to create a V-shaped inflow. The mixing action of the two designs was examined using Lagrangian particle tracking. Considerable influence of inlet configuration on the particle motion was observed. It was found that V-nozzles (two columns of inlet nozzles) are more effective than standard nozzles in flushing the solid particles.