A Macroscopic Approach for Simulating Horizontal Convection in a Vegetated Pond

A macroscopic approach for simulating horizontal convection in a vegetated
pond is presented. The generated convective currents are due to the differential radiation
absorption between the two regions of the pond, one with emergent vegetation up to the
free surface and one without vegetation. The Volume-Averaged Navier-Stokes (VANS)
equations are used for the simulation of the laminar, unsteady, two-dimensional horizon-
tal convection. The vegetation effects on the motion of the currents are taken into account
through additional resistance terms based on the vegetation porosity and permeability.
The Volume-Averaged Energy (VAE) equation is also solved with an additional source
term accounting for the absorption of radiation which is based on a one-waveband and a
three-waveband radiation model. The model setup is based on Beer’s law whereas the
incoming radiation is absorbed from the water column. Three types of vegetation
porosities φ varying from 0.75 to 0.97 are examined in investigating the motion of the
convective currents within the vegetated area. The case without vegetation (φ = 1.0) is
also examined for assessing the effectiveness of the radiation model. The numerical
current velocity and the water temperature increase are presented and compared against
available experimental data.