Flow–vegetation interaction in a compound open channel with emergent vegetation

Abstract

This study aims at revealing the flow structure in a vegetated compound channel with special emphasis on the interaction process and momentum exchange between the flow in the main channel and the vegetation that fully or partly covers the floodplain. A three-dimensional numerical simulation is carried out with a nonlinear k−ϵ model coupled with a vegetation model to explore the distribution of mean velocity and turbulence structure in the main channel and localized vegetation zones under emergent conditions. Laboratory experiments along with numerical simulations are carried out. Three types of vegetation zones are prepared on a floodplain of one side of the prismatic channel. The first type has an isolated vegetation zone that is 0.9 m long, the second type has two distant vegetation zones, each of which is 0.9 m long and these zones are 0.9 m apart, and the third type has fully covered vegetation zone that is 2.7 m long. The numerical results are compared against experimental observations in terms of mean velocities, showing a fairly good agreement between them.

Keywords:

• Vegetated compound channel
• flow structure
• nonlinear k−ϵ model
• localized emergent vegetation
• momentum exchange