ABSTRACT
Dense aquatic vegetation often plays an important role for river equilibrium, as it is a source of flow resistance promoting bed stabilization, controlling pollutant and nutrient transfer and providing a habitat for many aquatic species. These processes strongly depend on the two-way interaction between the mechanical behaviour of aquatic canopies and water flow. In this context, the present work investigates a single-row canopy made of plastic blades to model the behaviour of common macrophytes. Data from experiments in a narrow open channel and Large Eddy Simulations of the flow coupled to the unsteady blade motion via a proper robust Immersed Boundary Method are reported. The computations reproduce the blade reconfiguration quite accurately in a “static case” where the blades adopt a stationary, bent shape. Moreover, they provide detailed turbulence-resolving velocity data of the complex flow around the blades within the canopy responsible for the transfer processes named above. Secondly, a “dynamic case” with a higher flow velocity is considered, where the blades exhibit the so-called monami phenomenon. Experiments support a lock-in mechanism between blade oscillations and Kelvin-Helmholtz-like vortical structures. The simulations exhibit the same phenomenon, albeit with a larger spatial wavelength of the deformation. Instantaneous and statistical data are reported.
