Deciphering Morphological Changes in a Sinuous River System by Higher-Order Velocity Moments

Jyotismita Taye,Giuseppe Oliveto,Jyotirmoy Barman,Bimlesh Kumar

doi:10.3390/w12030772

Jyotismita Taye, Giuseppe Oliveto + Show 2 more

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https://doi.org/10.3390/w12030772

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Abstract

Bank erosion in a sinuous alluvial channel is a continuous phenomenon resulting in bank instability and migration of sediment. In this study, flume experiments were conducted in a sinuous channel to investigate its morphological changes and hydrodynamics. High-order velocity fluctuation moments are analyzed at outer and inner banks to explain the morphological variation in a sinuous river channel. The variance of streamwise velocity fluctuations on both banks of the sinuous channel follows a logarithmic law from a particular depth. In the outer bend region, the magnitude of velocity fluctuation moment is significant, indicating erosion. The trend of velocity fluctuation at higher even-order moments is similar to the variance of streamwise velocity fluctuations where the outer bend magnitude is greater than the inner bend. The premultiplied probability density functions (PDFs) and the flatness factor show greater magnitude in the outer bend of the channel as compared to the inner bend.

Highlights

The study of turbulence in a sinuous channel is a complex topic as compared to a straight channel.There is uniformity in a straight channel in both banks; in a sinuous channel, there are continuous erosion and deposition processes at outer and inner banks, respectively
Blanckaert [10] stated that the Reynolds shear stress (RSS) in a sinuous bend indicates the presence of helical flow, which contributes to the erosion and deposition processes
We observe that the magnitude of inner velocity is is more when compared to the outer bend of the channel throughout the flow depth. This result is more when compared to the outer bend of the channel throughout the flow depth. This result is similar to that found by the authors of the papers [3,12,38] who claimed that the velocity is greater in similar to that found by the authors of the papers [3,12,38] who claimed that the velocity is greater in the inner bend than outer because of velocity redistribution

Summary

Introduction

There is uniformity in a straight channel in both banks; in a sinuous channel, there are continuous erosion and deposition processes at outer and inner banks, respectively. Turbulence studies in a sinuous channel have been discussed quite elaborately over the past 2–3 decades. Researchers such as Rozovskiı [1], Anwar [2], de Vriend and Geldof [3], Blanckaert and Graf [4], Booij [5], Sukhodolov and Kaschtschejewa [6], and Engel and Rhoads [7] have studied the turbulent characteristics of both infield and laboratory and forwarded theories and articles regarding the uniqueness of flow behaviour. Blanckaert [10] stated that the Reynolds shear stress (RSS) in a sinuous bend indicates the presence of helical flow, which contributes to the erosion and deposition processes

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