Experimental and numerical investigation of the dynamic responses of longline aquacultural structures under waves

Abstract

Mariculture is an important activity in the exploitation of marine resources, of which longline raft culture accounts for a large part of the production. The flexibility due to the structural characteristics and the front-to-back shielding effect between suspended culture units have great influence on the dynamic response of the structure under waves. There are relatively few systematic studies on the impacts of this flexibility and shielding effect. Laboratory experiments are carried out in our work to investigate the dynamic response of different forms of aquacultural structures under the action of regular and irregular waves, in which the structural flexibility is reasonably considered and modeled. Then based on the experimental results, a numerical model developed in our previous work is optimized to take the shielding effect into account. Through the improved numerical model, the influence of structural parameters and wave parameters on the mooring line tension is analyzed. The results indicate that the shielding effect reduces with the increase of wave frequency. The maximum mooring line tension generally decreases with the decrease of culture density, and the decreasing trend is gradually weakened. The increase of anchoring angle results in a smaller maximum mooring line tension in most cases due to the reducing anchoring system constrains. The maximum value of the mooring line tension under the action of regular and irregular waves generally appears around the relative structure length B/L=1.15∼1.35. The conclusions of the experiment and analysis can be used as a reference for the design of similar longline aquacultural structures to avoid structural failure.