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Communication Dans Un Congrès Année : 2022

Erosion by an oscillating disc in the vicinity of a granular bed

Résumé

Flatfish, such as flounders, bury themselves in the sand to hide from predators. They are able to hide very quickly by oscillating their fins close to the seabed leading to the suspension of sand, which then fall onto their bodies. Our experimental set-up aims at reproducing while simplifying this natural behaviour. A rigid disc of diameter D and at an average distance H from a flat granular bed is set to oscillate at a frequency f (or period T) and an amplitude A such that the position of the disc is given by H + Asin(2πft). We study experimentally the erosion thresholds in the simple case of a half-oscillation, which means that the disc only moves downwards or upwards with smooth acceleration and deceleration. The influence of the relevant parameters, i.e. A, D and H as well as the initial position of the disc, on the erosion threshold is systematically characterized by finding the critical half-period τc = Tc/2 below which beads are set into motion. In the range of parameters considered in this study, the roll-up of the shear layer produced at the edge of the disc generates a vortex ring that is one of the main mechanisms responsible for the erosion of the granular bed. The key features of the vortex generated are then characterized by PIV (Particle Image Velocimetry) and related to the parameters of the experiments. The characterization of the fluid flow generated provides a better understanding of the erosion thresholds.
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Dates et versions

hal-04439546 , version 1 (05-02-2024)

Identifiants

  • HAL Id : hal-04439546 , version 1

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Joanne Steiner, Cyprien Morize, Alban Sauret, Philippe Gondret. Erosion by an oscillating disc in the vicinity of a granular bed. 5th symposium on two-phase modeling for sediment dynamics in geophysical flows (THESIS-2022), Jun 2022, Les Houches, France. ⟨hal-04439546⟩
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