Hydrodynamic modeling of kelp (Saccharina latissima) farms: From an aggregate of kelp to a single line cultivation system

With the expansion of macroalgae aquaculture in oceanic waters, especially of order Laminariales , a need exists to have optimized cultivation systems suitable for exposed conditions. To enable the design of such systems with a quantifiable level of confidence, in this paper, we developed a high-fidelity hydrodynamic modeling technique for kelp farms by introducing equivalent kelp elements for kelp aggregates with Reynolds number-based drag coefficients. After validating the model with towing tests for model kelp aggregates, it was then compared with comprehensive field datasets for a single line cultivation system with two mooring connections, in Saco Bay, Maine. The model yielded a larger tension than the measured tension by 23.3% on the west mooring line but a smaller tension by 23.2% on the east mooring line. The discrepancies may be caused by the uncertainties in the model configuration and input due to difficulties quantifying exact longline orientation, anchor-anchor distance, current reduction along the kelp longline, kelp mass density, and rope axial stiffness. Sensitivity analysis indicates that addressing these uncertainties may improve the model technique. Even though, the developed model is still reliable with a safety factor in the application for the design, installation and management of kelp aquaculture farms. • Reynolds number-based formulas for the drag area/coefficient of an aggregate of kelp are proposed. • Equivalent kelp element is validated with lab measurements for an aggregate of kelp. • Equivalent kelp element is validated with field measurements for a single line system. • Uncertainties in modeling the kelp farm are discussed in the context of both numerical modeling and field measurements.