Impacts of pool and vegetated banks on turbulent flow characteristics

Abstract

Bed forms and vegetation significantly influence flow characteristics. Macro-scale bed forms, such as pools, result in non-uniformity in flow; vegetation alters turbulence intensity, shear stress, and velocity distributions. To date, limited work on impacts of pools and vegetated banks on flow characteristics has been reported. Based on experiments carried out in laboratory, this study investigates the effects of pool and vegetated banks on flow velocity, Reynolds stress and turbulence intensity distributions. Results for a channel with pool and vegetated banks (vegetated-bank pool channel) are compared to those for channel with pool but without vegetation on pool banks (bare-bank pool channel). Results show that the combined impacts by vegetated banks and pools will intensify dip phenomenon and change the flow structure and its characteristics. It is also found that near both the pool entry and vegetated banks, estimation of the roughness coefficient is affected by the complex flow conditions. As a consequence, it is difficult to apply the Reynolds-averaged Navier-Stocks equations to interpret the results.