A Macroscopic Approach for Simulating Horizontal Convection in a Vegetated Pond

Abstract

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 horizontal 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. • Absorption of radiation based on one- and three-waveband attenuation models • Vegetation effects on the characteristics of horizontal convection • Effect of Grashof number on the motion of horizontal convective currents