Flow characteristics through submerged rigid vegetation over a sinusoidal perturbed bed

ABSTRACT

The flow through submerged, rigid vegetation on a sinusoidal bed is investigated. The steady, two-dimensional mass and momentum conservation laws in a porous media are solved using the perturbation technique. The rigid bed is approximated with sinusoidal function and its amplitude is assumed small compared to the total depth of the flow. The periodic bed considered in the study is similar to the equilibrium bedforms develop within vegetation array. Two fluid layers for the vegetated and non-vegetated zones are considered. Vegetation porosity is defined as the ratio of water volume with respect to the total volume of the vegetated layer. For the plane and sinusoidal bed, proposed model results compared well with previous studies. It is found that due to the perturbed nature of the bed, longitudinal and vertical velocity profiles follow a periodic pattern. A 180° phase of the vertical velocity with respect to the bed is observed. The vertical velocity is minimum at the crest of the perturbed bed and reaches maximum near the trough. In both layers, the magnitude of the longitudinal velocity is approximately an order of magnitude higher than the vertical velocity. Vegetation density causes a decrease in longitudinal velocity and increase in vertical velocity component. The amplitude of the periodic variation of bed shear stress increases, whereas the magnitude decreases with increase of vegetation density.

KEYWORDS:

• Rigid vegetation
• perturbation
• wetland
• vegetation porosity
• bed shear stress
• submerged vegetation