Instability of large-scale riverbed patterns

Ali, S K Zeeshan and Dey, Subhasish (2021) Instability of large-scale riverbed patterns. Physics of Fluids, 33 (1). pp. 1-15. ISSN 1070-6631

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In this paper, we explore the instability of large-scale riverbed patterns, performing a linear stability analysis of a zero-pressure gradient free-surface flow in a wide straight channel with an erodible bed. The local depth-averaged turbulence state is governed by two key parameters: Namely, the turbulent kinetic energy (TKE) and its dissipation rate. A depth-averaged flow model coupled with the transport equations of the TKE and its dissipation rate and the particle transport model are developed to examine the formation of large-scale patterns. Both the modes of particle transport as bedload and suspended load are considered herein, allowing for the extension of the conventional theories to cover from hydraulically smooth to transitional flow regimes. The classical Exner equation of the bed evolution is modified in the presence of suspended particles, whose concentration is coupled with the steady-state advection-diffusion equation. Applying a standard linearization technique, the periodic perturbations in both streamwise and spanwise directions are imposed on the bed to find the dispersion relationship. The stability maps for the growth rate of large-scale patterns are obtained as a function of streamwise and spanwise wavenumbers and of key parameters associated with the flow and particles. © 2021 Author(s).

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Item Type: Article
Additional Information: S.D. acknowledges the J. C. Bose Fellowship Award [funded by DST, Science and Engineering Research Board (SERB), Grant Reference No. JCB/2018/000004] in pursuing this work.
Uncontrolled Keywords: Advection-diffusion equation; Depth-averaged flows; Dispersion relationship; Periodic perturbation; Standard linearization technique; Transitional flow regimes; Turbulent kinetic energy; Zero pressure gradient
Subjects: Civil Engineering
Divisions: Department of Civil Engineering
Depositing User: . LibTrainee 2021
Date Deposited: 01 Sep 2022 04:50
Last Modified: 01 Sep 2022 04:50
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