Date of Award

Spring 2008

Project Type

Dissertation

Program or Major

Ocean Engineering

Degree Name

Doctor of Philosophy

First Advisor

M Robinson Swift

Abstract

Computational fluid dynamics (CFD) modeling, tow tank and field measurements were used to investigate current flow through and around net panels and cages. For the numerical computations a porous media model was used to represent the net allowing efficient computation of both exterior and interior flow fields. The model was calibrated using tow tank measurements on a net panel at different velocities and angles of attack. The CFD method was able to reproduce the drag- and lift coefficients of the net panel and the velocity reduction behind the net panel with satisfactory accuracy.

The approach was validated for a small size gravity cage by comparing CFD predictions with tow tank measurements of drag force on the cage and velocity reduction inside the cage and in the wake region. The modeled drag force was higher than the measured drag force. The modeled current compared well with the measured current inside the cage, but the reduction was underpredicted in the wake of the cage.

Full scale simulations were performed for a cage with a clean net and a biofouled net and compared with field measurements of a cage fouled with jellyfish. The measured data compared well with model predictions for the biofouled net. Flushing rates were calculated for both the clean and the biofouled net cases. When the net was changed from clean to biofouled, flushing time increased by up to 44% and drag force increased by up to 80%.

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