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Abstract

The netting of the fish farm, with biofouling or not, was simulated using the porous-media fluid model. The porous coefficients for both clean and biofouled netting were calculated from the drag and lift forces that acts on corresponding clean or biofouled plane net, consequently the relationship between the porous coefficients and the features of the netting as well as the biofouling is established. In this study, both constant and tidal currents through a fish farm, consisting of 2×4 full-scale net cages, were investigated numerically. Effects of cage height, incidence angle of the current and level of biofouling on the netting on the flow field in vicinity region of the fish farm were presented and discussed. Compared with constant current, tidal current produces different flow pattern downstream from the fish farm. Overall, the height of the wake region downstream from the fish farm increases with increasing cage height. The attenuation in flow velocity both inside the net cage and in the wake region increases as the level of biofouling increases. With respect to the incidence angle of the tidal current, the optimal orientation of the fish farm can be determined in certain tidal current from an ecological perspective.

Examination of net volume reduction of gravity-type open-net fish cages under sea currents

“…The effect of flow velocity reduction factor, which can be changed due to various reasons Bi, et at., 2014;Zhao, et al, 2013), was also examined. For example, biofouling commonly happens to fish cages in seawater with biological layers attached to the net surface, leading to an increase in the flow velocity reduction factor u C , i.e., the flow velocity for the rear part of the fish cage is reduced due to biofouling (Bi et al, 2017;Bi and Xu, 2018). The volume reduction factors v C for circular cylinder fish cages under a changing flow velocity reduction u C are shown in Table 7 with 0.18 u C = as the baseline factor in this comparison.…”