Hydrodynamics induced by an artificial suspended canopy with limited length and width, which imitates a real world shell fish farming structure, have been studied. Laboratory experiments and numerical simulations have been adopted to study the features of the flow field. In the laboratory, physical models of suspended canopies with different densities and canopy elements arrangements were towed through a large tank. Acoustic Doppler Velocimeter (ADV) was used to measure the flow velocities along the two sides and behind the suspended canopies and a load cell was used for the measurement of the total drag forces created act that on the suspended canopies. The OpenFOAM package was used to perform numerical simulations. The experimental results were used to validate the results obt...[ Read more ]

Hydrodynamics induced by an artificial suspended canopy with limited length and width, which imitates a real world shell fish farming structure, have been studied. Laboratory experiments and numerical simulations have been adopted to study the features of the flow field. In the laboratory, physical models of suspended canopies with different densities and canopy elements arrangements were towed through a large tank. Acoustic Doppler Velocimeter (ADV) was used to measure the flow velocities along the two sides and behind the suspended canopies and a load cell was used for the measurement of the total drag forces created act that on the suspended canopies. The OpenFOAM package was used to perform numerical simulations. The experimental results were used to validate the results obtained from the simulations.

The features of the flow induced by the suspended canopy were similar to those induced by emergent and suspended canopies of limited length and width and using the canopy-related hydraulic radius Reynolds number, results for the drag coefficient for all three canopies collapsed onto a single line. At the same time the features were significantly different from the flow features generated by canopies of essentially infinite size which have an interior zone where the flow is fully turbulent, steady and uniform. The limited length of the canopies studied meant the interior was not reached and estimates for shell fish farming structures indicate that this is common in the real world as well.

Analysis of the detailed results showed that the flow blockage which depends on the density of the suspended canopy and the effective projected area related to the canopy element arrangement controls the behavior of the flow field. It affects the diversion of flow around and below the canopy, decrease of the velocity within the canopy, length of the constant velocity and velocity recovery zones in the wake, generation of the turbulence due to the canopy elements and shear layers at the sides and bottom of the canopy, the total drag forces, and the bulk drag coefficients. The length of the suspended canopy impact zone and total wake zone were the only two parameters that did not depend on the density and the canopy element arrangement but only on the width of the suspended canopy. Flow fields generated by two upstream velocities of 0.10 m/s and 0.20 m/s, gave very similar results as the flow field depended only weakly on the canopy Reynolds number.