Abstract
The paper is partly a review on hydrodynamic and structural aspects offish farms. In addition, new numerical results are presented on the stochasticbehavior of bending stresses in the floater of a realistic net cage in extreme waveconditions. The behavior of traditional-type fish farms with net cages and closedfish farms in waves and currents is discussed. Hydroelasticity can play asignificant role for net cages and closed membrane-type fish farms. The many meshesin a net cage make CFD and complete structural modeling impracticable. As anexample, a hydrodynamic screen model and structural truss elements are instead usedto represent the hydrodynamic loading and the structural deformation of the net. Inaddition, the wake inside the net due to current plays an important role. Thedescribed simplified numerical method has been validated by comparing with modeltests of mooring loads on a single net cage with two circular elastic floaters andbottom weight ring in waves and currents. It is discussed which parts of thecomplete system play the most important roles in accurately determining the mooringloads. Many realizations of a sea state are needed to obtain reliable estimates ofextreme values in a stochastic sea. In reality, many net cages operate in closevicinity, which raises questions about spatial variations of the current and waveenvironment as well as hydrodynamic interaction between the net cages. Live fishtouching the netting can have a non-negligible influence on the mooring loads. It isdemonstrated by numerical calculations in waves and currents that a well boat at anet cage can have a significant influence on the mooring loads and the bendingstresses in the floater. The latter results provide a rational way to obtainoperational limits for a well boat at a fish farm. Sloshing has to be accounted forin describing the behavior of a closed fish farm when important wave frequencies arein the vicinity of natural sloshing frequencies. The structural flexibility has tobe considered in determining the natural sloshing frequencies for a membrane-typeclosed fish farm. Free-surface non-linearities can matter for sloshing and can, forinstance, result in swirling in a certain frequency domain for a closed cage with avertical symmetry axis.
Highlights
The expected increase in the world population requires more food
Many net cages operate in close vicinity, which raises questions about spatial variations of the current and wave environment as well as hydrodynamic interaction between the net cages
New numerical results are presented on the stochastic behavior of bending stresses in the floater of a realistic net cage in extreme wave conditions
Summary
The expected increase in the world population requires more food. There is a large potential in increasing the marine food. Shen: Wave and Current Effects on Floating Fish Farms salmon may breed with the wild salmon and lead to genetic pollution of the wild fish. We start with discussing wave and current loads on floating fish farms with net cages and go on to study closed fish farms. The influence of a well boat at a floating fish farm with net cage in waves and currents is part of the analysis. A bottom weight ring (sinker tube) is often used instead of bottom weights to ensure sufficient volume of the net cage. A consideration is minimum net deformation to ensure sufficient net cage volume. Large snap loads due to the elastic behavior of the net structure and the relative motion between the floater and the net can occur. Bardestani and Faltinsen (2013) experimentally and numerically predicted the latter fact in nearly 2D flow conditions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
