Numerical Modeling for an In Situ Single-Point-Mooring Cage System

To mitigate marine pollution intensity at the sea bottom, an automatic rotating type of cage systems such as a single-point-mooring (SPM) cage system is often regarded as biofriendly equipment for fish farming in the open sea due to spreading uneaten waste feed and fish feces into a vast area. Though the SPM cage dynamic features under regular sea state have been investigated in previous researches, the in situ sea state is by no means a regular one, thus a further exploration of the dynamic response in the random sea is critical before deploying cages into the open sea. This work developed a numerical model for irregular sea states to simulate an SPM cage system in an unsheltered open sea, considering the environmental conditions as irregular waves combined with a steady uniform current. To validate the numerical model, a full-scale physical model was tested in the field, where both sea states and mooring line tension were recorded. Results indicate that the numerical model predictions have good agreement with field measurements in both time and frequency domains, while the net-volume deformation is presented numerically to show fish net space variation in a random sea.