Author(s): Edwin Saavedra-Cifuentes, Antonio Preziosi-Ribero, Jorge Alberto Escobar-Vargas, Leonardo David Donado
Linked Author(s): Edwin Saavedra Cifuentes
Keywords: Hyporheic zone, numerical simulation, apparent viscosity, surface water � groundwater interaction
Abstract: Several recent advances have been made on the development of numerical simulations for the flow dynamics on the hyporheic zone of rivers, generally for the interaction of a channel flow over a permeable bed, where the mixing of surface and subsurface water is evident. This work has taken into account a quick revision of the different conceptual and numerical applications of these advances, identifying their different assumptions and simplifications, such as unidimensional models of velocity fluctuation and coupled models of turbulent and laminar flow regimes. Special interest is shown in how the interface between the turbulent surface flow and the laminar flow in the porous media is managed, and the impacts of the imposed boundary conditions on the velocity and pressure fields. Consequently, a two-dimensional numerical model has been proposed and implemented in the CFD package OpenFOAM� adopting the existence of pressure and velocity fluctuations coming from the turbulent surface flow of an idealized river, assuming a whole uninterrupted computational domain containing both surface and porous flows, and characterizing the porous river bed using an apparent viscosity as a continuous space that represents the tortuosity of the flow inside the porous matrix. The case of study is a flow over a trapezoidal obstacle in order to visualize and quantify the dissipation of the velocity when entering into the porous bed, as well as to characterize the flow path within the hyporheic zone. Finally, a discussion is made on the evident impact of the different initial and boundary conditions evaluated, and on the nature of the transitional damping zone of the velocity and pressure fluctuations between the surface and porous spaces
Year: 2017