Flow structure along the cross-section of an open-channel caused by patch of submerged vegetation

Vegetation is crucial part of ecosystem in natural rivers. the flow structure changed mostly in streamwise, lateral, and vertical directions because of the kelvin-helmholtz instability caused by vegetated canopy. in this study, the flow characteristics under the effect of limited-length submerged vegetation patch were investigated experimentally. the rigid submerged vegetation layer with 1.2 m length, 0.6 m width were used to simulate limited-length submerged vegetation patch in the experiments. the vegetation layer was composed using rigid circular plastic dowels with 0.01 m diameter and 0.05 m height. two different vegetation densities which are 𝑁1=161 ipm^2⁄ and 𝑁2=1149 ipm^2⁄ were used to obtain the effect of vegetation density. the velocity measurements were performed using adv. according to the results obtained, the presence of vegetation causes strong gradient in the flow structure over the cross-section of the channel. higher vegetation intensity causes higher velocity gradient in the velocity distribution. additionally, “s-curve” shaped depth averaged stream-wise velocity profile was obtained along the cross- section with steeper curve for higher vegetation intensity. turbulent kinetic energy was obtained higher in the vegetated part comparing to non-vegetated part. furthermore, turbulent kinetic energy peak occurs at the vegetation interface between inner and outer layer in the vegetated part for higher vegetation intensity. beside this, strong momentum exchange appears at the interface between the inner layer and outer layer at the vegetated part for higher vegetation intensity. the discharge capacity of the channel was also examined and found that discharge capacity decreases with increasing vegetation density.