Modelling of Drag Forces on a Closed Flexible Fish Cage

To cope with ecological challenges in the aquaculture industry, Closed Flexible Fish Cages (CFC) are proposed used in the sea. However, the existing knowledge about how the CFC will respond to external sea loads are limited. More knowledge is needed to understand the response of the cage if this technology is to be utilized in an industrial scale. In this paper a new method for mathematical modelling of the increase in drag, for decreasing filling level of a CFC is proposed. A model for a filling-level-dependent drag coefficient is presented. Experimental data are analysed related to forces and deformations on the bag for different filling levels. The analysed bag showed an increased tendency to deform for decreasing filling levels, leading to an increase in drag coefficient.