Preliminary experimental investigation on the interaction of a subaqueous dune like granular structure with a turbulent open channel flow

International Center for Theoretical Sciences, Tata Institute of Fundamental Research, Bengaluru 560089, India

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Published online: 1 December 2025

Abstract

We study the interaction of a subaqueous dune like granular structure with a turbulent open channel flow experimentally using optical diagnostics in the Shields and Froude parameter space (0.05≤θ≤0.32, 0.1≤Fr≤0.4). Interactions between the turbulent flow and the granular structure give rise to transient erosiondeposition dynamics leading to various types of particle transport. The subaqueous structures in the channel bed evolves due to shear-stress-induced erosion, gravity-driven deposition, and subsequent particle transport. We study the centroid motion and the granular structure shape evolution. At lower end of our θ − Fr parameter space, we observe no erosion and the structure remains at rest. We show that the critical Shields number (θ_cr) is of the order of 0.1 beyond which erosion starts to occur. At intermediate values of θ and Fr we observe slow erosion, resulting in a rigid body motion of the granular structure without significant shape deformation. Higher values of θ and Fr causes vortex formation at the upstream of the dune resulting in stronger erosion, rapid shape deformation and relatively higher translation velocity of the centroid.