On the effect of filament inclination on the different regimes of canopy flows

We have performed high-fidelity simulations of turbulent open-channel flows over submerged rigid canopies made of cylindrical filaments of fixed length h/H = 0.1 with mean spacing of S/H = 0.066 (with ‘H’ being the open channel height). The filaments are flush mounted perpendicular to an impermeable wall. The shape of the canopy was modulated by changing the inclination of the filaments (angle formed by the filaments with the mean streamwise direction) thus modelling the deformation of very soft filaments under the action of a unidirectional mean flow. The inclination, used as a free parameter, dictates the solidity of the canopy, yielding to different flow regimes (sparse or dense). The effect induced by inclining the canopy can also be interpreted as a modulation of the diagonal elements of the permeability tensor the canopy seen as a porous medium. These changing conditions lead to new flow regimes configurations that, so far have not been described in the literature. We have considered six inclinations in the range θ between 0° and 90°, with θ = 0° and θ = 90°, representing normal wall mounted and wall parallel conditions. We find that when the canopy is inclined, the behaviour of the flow (inner and outer) exhibits a drastic changes that cannot be predicted using the notion of solidity as unique parameter that determines the flow behaviour.