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Special Topics & Reviews in Porous Media: An International Journal
ESCI SJR: 0.277 SNIP: 0.52 CiteScore™: 1.3

ISSN Print: 2151-4798
ISSN Online: 2151-562X

Special Topics & Reviews in Porous Media: An International Journal

DOI: 10.1615/SpecialTopicsRevPorousMedia.2017019609
pages 91-108

NUMERICAL SIMULATION OF CONVECTIVE CURRENTS IN AQUATIC CANOPIES USING A MACROSCOPIC MODEL

Maria Tsakiri
Hydraulics Laboratory, Department of Civil Engineering, Aristotle University of Thessaloniki, Thessaloniki, 54124, Greece
Panayotis Prinos
Hydraulics Laboratory, Department of Civil Engineering, Aristotle University of Thessaloniki, Thessaloniki, 54124, Greece

ABSTRACT

In the present study, convective currents between open water and aquatic canopies are numerically investigated using a macroscopic model. The convective currents are produced due to differential radiation absorption between the two regions. The unsteady two-dimensional volume-averaged Navier-Stokes equations are used and the vegetation effects are taken into account through additional resistance terms using a porous media approach based on porous medium permeability. The model can be used even for vegetation with a complicated structure (stems, foliage) in which the vegetation permeability k can be easily determined. Seven cases with vegetation porosity φ from 0.75 to 0.97 and one case without vegetation are examined to investigate the vegetation effects on the motion of the convective currents. Thus, cases with low vegetation porosity (φ < 0.85) are also investigated, in which there is no sufficient information. A microscopic model, which uses the unsteady three-dimensional Navier-Stokes equations to simulate the flow characteristics around individual vegetation elements, is also used for comparison purposes. The energy equation is also solved in both models, in which the absorption of radiation is taken into account through an additional term. The Boussinesq approximation is applied to take into account the density difference due to the temperature difference. The numerical results for the current velocity and water temperature obtained from both models are presented and compared against available experimental data. Empirical relationships between the current velocity and vegetation porosity are also derived, which can be used for further investigation.


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