Characteristics of turbulent flow in 3-D pools in the presence of submerged rigid vegetation in channel bed

Abstract

In this study, the interaction between 3-D bedforms and submerged rigid vegetation has been investigated. Various laboratory experiments were conducted to study the distribution of flow velocity, Reynolds shear stress, turbulent kinetic energy, and skewness coefficients for a constant density of vegetation. Results showed that the velocity profile in the pool section deviates from those in the upstream section of the pool. It has been found that the dip parameter varied between 0.6H and 0.9H depending on various factors including bed roughness, vegetation distribution, and pool entrance/exit slopes. However, scattered vegetation in the pool and differences in slopes created non-uniform flow conditions. Also, in the wake region behind each vegetated element, flow velocity reduced significantly, and small-scale eddies are formed, causing increased perturbations. By decreasing the entrance slope and bed roughness, relatively uniform flow and weaker turbulence was resulted, but the random distribution of vegetated elements counteracted this balance and intensified turbulence. With the decrease in the pool entrance slope, the contribution of sweep event decreased and the contribution of ejection event increased.