Numerical Study on Hydroelastic Responses of Submersible High-Density Polyethylene Circular Seaweed Platforms Held by Single-Point Mooring System and Buoys

Abstract

This paper investigates the hydroelastic behavior of submersible circular seaweed platforms under wave action. The circular platform comprises circular collars constructed from high-density polyethylene (HDPE) pipes and seaweed grow-out lines arranged in the radial direction. The HDPE pipes may be filled with air, seawater, or pressurized seawater. The platform is kept in place by using a single-point mooring system and buoys. The platform may be lowered to over a hundred meters below the water surface to allow the seaweed to be soaked in cold nutrient-rich waters during the night and be raised to the surface for photosynthesis during the day. Also, the platform will be submerged during storms to avoid strong surface waves. The submergence is achieved by using a service vessel and surface buoys that secure the submerged platform with ropes. The hydroelastic analysis of the platform is performed using AquaSim software (v. 2.18), which has been developed specifically for hydroelastic analysis of aquaculture infrastructure. It is found that the hydroelastic response of the seaweed platform can be reduced by filling HDPE pipes with seawater and through the installation of seaweed grow-out lines. It is also found that the compressive stresses in HDPE pipes can be reduced by pressurizing the filled seawater, thereby keeping them below the allowable compressive stresses for severe sea states where pipes with unpressurized seawater show excessive compressive stresses.