A Numerical Model To Evaluate Flow Characteristics In A Circular Vegetation Patch For Flume Experiments

A 2D numerical model was performed for the flume experiments to clarify the combined effect of the vegetation patches mimicked by circular cylinders attached vertically in a laboratory canal with different bed roughness on the flow characteristics. Eleven patches with numbers of cylinders were distributed uniformly at a distance of 0.20 m center -to -center along the flume length starting from 1.2 m from the flume entrance. The combined effect of the vegetation patch and bed materials on the drag coefficient Cd, the velocity distribution, and turbulent kinetic energy has been investigated using computational fluid dynamics. A mathematical model was established using the experimental data available in the literature. Results showed good agreement between the experimental and numerical drag coefficients by the vegetation patch and for the different bed roughness with a correlation coefficient of more than 99%. Results also showed a high correlation coefficient for all the laboratory experiments between Cd and n. One of the main problems with this type of flow is that vortices are strongly influenced by the adjacent cylinders downstream. Clear differences in velocity distribution and turbulent kinetic energy through the patches for the various bed materials have been monitored. The turbulent kinetic energy within the patch is increased by 2-3 times downstream of the patch. In this computational numerical domain, the simulation of the flow velocity in open channels with and without vegetation elements is well captured within and downstream of the patch and the wake by the individual cylinders.