Calibration of a 3D hydrodynamic aquaculture model

Abstract

Aquaculture structures comprising suspended canopies extending from the free surface to a point above the sediment are represented as porous blockages in a hydrodynamic surface-water model. These canopies alter flow conditions and material transport within and around the structure, especially between the bottom of the canopy and the sediment bed. These altered flow conditions can have significant implications for sediment, nutrient, and waste transport in the environments in which aquaculture structures are placed. This study uses an augmented version of the Environmental Fluid Dynamic Code to model flow conditions in and around a suspended canopy calibrated against data obtained from a series of flume tests. The parameter estimation code, PEST, was used to calibrate various model parameters including horizontal momentum diffusivity, vertical eddy viscosity, turbulence closure constants, and depth-dependent drag coefficients to ensure that model simulations match the experimental (calibration) data comprising vertical velocity and turbulent kinetic energy profiles. The model was then validated against vertical profiles of turbulent kinetic energy production rate, which were not used during the calibration process. Ultimately, trends of increasing average drag coefficient with decreasing canopy blockage ratio and increasing average flume flow speed were observed. The calibrated canopy-turbulence parameters may yield improved predictions of the hydrodynamic and material transport conditions resulting from the various aquaculture structures and flow systems. In turn, these predictions will help develop methods to minimize environmental impacts and to increase production from aquaculture farms.