Turbulent flow mechanisms in meandering channels with sediment transport

Abstract

This research aims to investigate the near-bed turbulent flow characteristics in a meandering channel with both mobile bed and immobile bed conditions. Experiments were performed in a prismatic rectangular meandering channel with a non-uniform sand bed of size d50 = 0.523mm. The three-dimensional instantaneous fluid velocity was collected using the Acoustic Doppler velocimeter which will provide important results related to the flow turbulence such as mean flow velocity, turbulence intensity, Reynolds shear stress, turbulent kinetic energy, skewness, kurtosis and turbulent anisotropy. The secondary current flow and the exchange of momentum in the form of turbulence kinetic energy, Reynolds shear stress and turbulent intensity at the inner layer of the flow are identified more in a mobile bed condition as compared to an immobile condition, which causes sediment transport. For the inner layer of the flow, turbulence intensity and turbulent kinetic energy are decreased in magnitude and gradually increase in the outer layer of flow for both the bed conditions. Higher turbulence anisotropy is noticed in the mobile bed condition than in the immobile bed condition, which shows more nonuniformities near the bed level for the mobile bed condition. This study may help in understanding the effect of sediment transport due to a turbulent flow structure in a sinuous alluvial channel.

Physical and Numerical Modeling of Flow in a Meandering Channel

“…In our study, the meandering channel's geometry with successive 180 • and 120 • bends with different angles, and the extended approach channel distinguishes it from other channels studied in the literature, which typically feature more uniform or less extreme bend angles. The experimental model in many studies in the literature consists of only a single bend or narrow-angle uniform sinusoidal bends [1,[4][5][6][7][9][10][11][12]14]. In this study, the fairly long approach channel also ensures the flow reaches fully developed flow conditions before entering the meanders.…”

“…Dombroski and Crimaldi evaluated the accuracy of ADV velocity measurement data in turbulent boundary layer flow over a hydraulically smooth surface [8]. Sahoo and Sharma studied the turbulent flow mechanism in meandering channels using the ADV technique [12]. Laboratory studies performed by Ishigaki et al and Bai et al with PIV can be shown as other example studies for understanding flow behavior in a meandering channel [13,14].…”