Abstract:
The main goal of this study is the 3D numerical simulation of river flows with
submerged vegetated floodplains. Since, vegetation layers are usually dense and present a
large spatial heterogeneity they are here represented as a porous media. Standard semiempirical
relations drawn for porous beds packed with non-spherical particles are used to
estimate the porous media parameters based on the averaged geometry of the vegetation
elements. Thus, eliminating the uncertainty arising from a bulk drag coefficient approach
and allowing the use of a coarser mesh. The free flow is described by Reynolds-averaged
Navier–Stokes (RANS) equations, whereas the porous media flow is described by the
volumetric-average of RANS equations. The volume-of-fluid method and an anisotropic
explicit algebraic Reynolds stress model are used for free-surface and turbulence closure,
respectively. The simulation approach is validated against results by other authors featuring
vegetated flows in horizontal and rectangular open-channel. The computed results
show that the time-averaged streamwise velocity and Reynolds shear stress vertical profiles
are properly simulated. The validated approach was applied to simulate compound openchannel
flows with submerged vegetated floodplains and compared with data obtained in
an experimental facility. The results show that the proposed porous media approach is
adequate to simulate flows with submerged vegetation on the floodplains.
