Author(s): Sofi Farazande; Christophe Ancey

Linked Author(s): Christophe Ancey

Keywords: Antidunes; Turbulence; Supercritical flows; Velocimetry

Abstract: River bedforms such as dunes, antidunes, steps and pools arise from flow instabilities, and their features are determined by both flow conditions and bed characteristics. In most cases, dunes are observed under subcritical flow conditions, while antidunes appear under supercritical conditions. The interaction between these bedforms and the flow field, especially in supercritical regimes, is not yet fully understood. Models based on the shallow-water equations include skin friction (i.e., turbulent dissipation caused by bed roughness), but usually ignore the extra stress created by the bedforms. For one-dimensional flows, the momentum balance equation of the shallow-water equations can be cast in non-conservative form (1): h∂u/∂t + u∂u/∂x + gh∂h/∂t = −gh sin θ − τb/ρ, where h is the water depth, u is the flow velocity, g is gravitational acceleration, θ is the bed inclination angle, τb represents the bed shear stress, and ρ is the water density. While the term −τb/ρ accounts for bed roughness-induced friction, it does not explicitly capture the dynamic effects of bedform-induced stresses. In light of these complexities, the present study conducts experimental investigations to better understand how antidunes affect the flow field.

DOI:

Year: 2025