The Influence of Slot Design and Biofouling on the Hydrodynamics and Dissolved Oxygen Exchange Through a Finfish Open Ocean Aquaculture Structure

Abstract The current study examines the influence of a new design of open ocean aquaculture (OOA) finfish structure and environmental and physical factors on the hydrodynamics and dissolved oxygen (DO) exchange using Computational Fluid Dynamics (CFD). The structure is a 1,500 m3 square cross-section cylinder with mesh placed at the front and back of the body. There are slots on the body of the structure with densities varying between 0% (i.e. no slots) and 12%. Both parallel and perpendicular to the flow direction slots are examined. Biofouling is simulated using a flow reduction ratio through the mesh that varies between 5% and 50%. Fish density is 15 kg.m−3 and water temperature is 15°C with current speed scenarios of 0.1, 0.05 and 0.01 ms−1. We found that increasing the flow reduction ratio through the mesh to simulate biofouling effects results in a decrease of DO inside the structure. For example, flow reduction through the mesh increases from 15% to 50% resulting in the healthy volume fraction inside the structure (i.e. DO 70% saturated DO) decreases from 0.22 to 0.15, when current speed is 0.01 ms−1. Increasing slot density facilitates flow ventilation through the structure and increases DO inside the structure. Increase of current speed results in an increase of DO inside the structure. For example, the healthy volume fraction increases from 0.19 to 1.0 when the current speed increases from 0.01 to 0.1 ms−1. Overall, we found that CFD modeling is a useful tool to explore the complex relationship between novel OOA structure designs (e.g. various slot densities on the body of structure) and environmental and physical factors (e.g. blockage mesh effects, current speed) on the hydrodynamics and DO exchange.