Numerical modeling of drag for flow through vegetated domains and porous structures

In this paper, we study flow through vegetated wetlands using high resolution computational models to describe the flow. The goal is to describe drag characteristics of this flow at the large scales as a function of Reynolds number. This work is of importance to scientists and engineers dealing with wetland health and restoration, inland flooding due to tropical storms and hurricanes, and river lining projects. The existence of vegetation affects the flow resistance, which is a major factor in determining velocity and water level distribution in wetlands. For low Reynolds numbers, wetlands behave similarly to porous media, where it is well-known that Stokes flow at the micro-scale can be upscaled through homogenization to Darcy’s Law at the macro-scale. As Reynolds number increases moderately, small-scale drag effects can be captured by adding a quadratic and/or cubic term to the Darcy equation; the so-called Darcy–Forchheimer model. For higher Reynolds numbers, Stokes equation is no longer a valid approximation, and full Navier–Stokes models must be used. We utilize large eddy simulation (LES) to study vegetative drag at high Reynolds numbers. The numerical simulations in this paper are performed using the Proteus Toolkit, which is under development by Kees and Farthing at ERDC.