| dc.description.abstract | The aquaculture industry in Norway is experiencing significant growth and is becoming one of the country’s largest export industries. However, this growth causes environmental concerns, such as salmon lice, organic waste, and unstable conditions in open fish farms, including fluctuating temperatures and oxygen levels. To address these issues, new technologies are being developed. Ovum AS, with its Egget® design, is tackling challenges in current fish farms with a closed design. These designs increase hydrodynamic loads compared to open fish farms, making both experimental and theoretical analyses essential for understanding their hydrodynamic behaviour.
This master’s thesis aims to develop a measurement unit to acquire the hydrodynamic response of Egget®. This unit will measure accelerations, angular velocities, and geographical positioning. By analysing the hydrodynamic response, numerical analysis data of Egget® is compared with full-scale data, providing an accurate representation without the scaling effects seen in model experiments. Additionally, GPS data on low-frequency oscillation periods allows for the evaluation of Vortex-Induced Motion (VIM).
Results of the investigations into VIM indicate that the oscillation period measured from GPS data corresponds to a realistic theoretical current velocity at the measurement location. Calculations suggest that lock-in is unlikely. Therefore, while VIM is a potential concern for Egget® at its location, the occurrence of lock-in is improbable.
The hydrodynamic response analysis focused on three Degrees of freedom: heave, roll, and pitch. Two 3-hour measurement samples were selected based on wave hindcasts. Results indicate that the largest roll and pitch responses occur in the sloshing period, while higher periodic waves at the heave eigenperiod dominate the heave response. Additionally, smaller responses in the roll eigenperiod and pitch responses with a 1 s delay to its eigenperiod were observed.
Numerical analyses of Egget® were conducted and compared with full-scale experiments. Using wave hindcasts, two reverse-engineered sea states were created for the experimental samples. These sea states were realistic given earlier wave measurements and expected wave directions. Comparing numerical data with full-scale experiments showed that roll and pitch responses were fairly accurately predicted, while the heave response was underestimated. | |
