Parameterizing suspended canopy effects in a three-dimensional hydrodynamic model

This paper presents an amendment of an existing three-dimensional hydro-environmental model (Environmental Fluid Dynamics Code) to incorporate effects of suspended canopies on the vertical flow structure. Five different modelling approaches are investigated, encompassing hydrodynamic form drag imparted by the suspended canopy, an amended two-equation turbulence scheme representing turbulence generated locally by elements within the canopy, and three separate formulations for vertical profiles of drag coefficients. Data from laboratory experiments with rigid cylinders are used to validate the calculations of velocity and shear stresses. The results show that the most accurate reproduction of the canopy flow was obtained using a vertically varying drag coefficient along with a two-equation turbulence closure scheme that includes additional turbulence production and dissipation terms. The numerical model reproduced velocity profiles accurately, but the shear stresses are slightly overestimated.