Three-dimensional deformation of a large circular flexible sea cage in high currents: Field experiment and modeling

• Issues related to flow around fish cages with respect to design and fish behavior.
• Main interactions: current flow/net cage and current flow/fish.
• Deformation of large flexible porous system.
• 3D dynamic super-element formulation simulation.

This paper presents the full-scale measurements of the deformation and current reduction of a large-scale fish sea cage submitted to high currents. Pressure tags were used to measure the cage deformation and the vertical displacement of the bottom ring, while an Acoustic Doppler Current Profiler (ADCP) and Acoustic Doppler Velocimeter (ADV) were used to measure the current reduction. The results show a reduction of 30% of the cage volume for current velocity above 0.6 m/s. The measured current reduction in the cage was 21.5%. A simulation model based on super-elements describing the cage shape was applied, and the results show good agreement with the cage deformations. Also the current flow measurements show the interaction between the sea cage and the bathymetry chart.