Experimental Study on the Near-Bed Flow Characteristics of Alluvial Channel with Seepage

Anurag Sharma,Giuseppe Oliveto,Bimlesh Kumar

doi:10.3390/app11209619

Abstract

This paper aims to analyze the turbulent structure of flows over beds undergoing downward seepage under clear-water conditions. Laboratory experiments in this regard were carried out in a straight rectangular channel that was 17.20 m long and 1.00 m wide. A sandy bed with median grain size d50 = 0.50 mm and sediment gradation σg = 1.65 (i.e., slightly non-uniform sediment) was used for the channel bed. The 3D instantaneous velocities of water were measured with an Acoustic Doppler Velocimeter (ADV) at the working test section. In the vicinity of the bed surface with seepage, measurements revealed that the flow longitudinal velocities (i.e., velocities in x direction) were higher than those in the case of a bed without seepage. Moreover, the variations inthe Reynolds shear stresses increased for the bed with seepage, indicating a higher exchange of flow energy towards the boundary and vice versa. Therefore, it was found that seepage processes influence the turbulence intensity, with a prominent magnitude in the streamwise and vertical directions. The paper also focuses on the third-order moment (skewness) and the kurtosis of velocity fluctuations and the governance of sweep events within the near-bed flow in cases where seepage was observed.

Highlights

The structure of turbulence was achieved based on the Acoustic Doppler Velocimeter (ADV) data
Laboratory experiments conducted to detect the turbulent characteristics of on the turbulent characteristics in the presence of seepage led to various conclusions
An Acoustic study of the vertical distributions for the mean velocities revealed that the velocities at the Doppler Velocimeter (ADV) was used to measure the instantaneous velocities of flow

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The flow interaction with the sediment in a river might cause bed aggradation and degradation processes, which are essential in river control engineering. One of the most important characteristics of a fluvial bed is the movement of the water through the soil in terms of downward seepage because of soil permeability. The channel bed distortions and the turbulent flow features are altered in the presence of downward seepage flow (seepage through the channel in the downward direction) [1].The seepage and related turbulent dynamics play an important role in the solute transport across the hyporheic area in rivers [2].This aspect could have important implications for groundwater quality

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