Hydrodynamic and harvesting operation analysis of a longline for aquaculture

November 26, 2025

This thesis presents a comprehensive hydrodynamic analysis of a longline aquaculture system designed for offshore bivalve cultivation under regular wave conditions. The study employs a lumped mass model- ing approach using OrcaFlex as the primary simulation tool, with wave kinematics computed according to linear Airy wave theory. A systematic investigation is conducted to assess the influence of wave height, wave period, deployment depth and wave heading on anchor tension and lantern motion characteristics. Results demonstrate that deployment depth provides exponential attenuation of wave induced load- ing, reducing anchor tensions by 50% when increasing depth from 8 m to 18 m under 6 m wave con- ditions. Wave period exhibits strong inverse correlation with system loading. Lantern motion analysis reveals that horizontal displacements show stronger depth dependency than vertical components, with wave period emerging as the dominant parameter governing motion amplitude and inclination. Harvesting operation modeling demonstrates significant dynamic coupling between the vessel and cultivation infrastructure, with anchor tensions increasing from 20 kN for the isolated system to peak values exceeding 65 kN during extraction operations. The findings provide quantitative design guidance for optimizing longline systems in exposed offshore environments, identifying critical parameters that govern structural integrity and operational performance

Authors in the community:

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  R

  Riccardo Chini

  ist1108376

Supervisors of this institution:

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  S

  Susana Margarida da Silva Vieira

  ist45346

mechanical-engineering - Mechanical engineering

eng - English

Instituto Superior Técnico