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Skimming transition in flexible granular sweeping

Y. Ochi, H. Katsuragi

cond-mat.softarXiv:2608.15069

Abstract

A flexible body placed in a steady flow bends to reduce drag. This self-streamlining is a hallmark of fluid-structure interaction (FSI). Granular-structure interaction is equally ubiquitous in nature. However, it remains poorly understood. Thus, we investigate inertial granular-structure interaction (IGSI). Specifically, ejection induced by a flexible plate sweeping a granular bed is experimentally examined. We find that a faster sweep results in less ejection, particularly for a flexible plate. To understand the underlying physics of this behavior, a dimensionless number Sk is introduced as the ratio of the plate elastic timescale to the sweep timescale. At Sk 1, the plate deflection follows the self-streamlining law of FSI and induces substantial ejection. At Sk 1, on the other hand, the plate skims the bed and the mass of ejected grains decreases sharply. Sk organizes IGSI as the granular counterpart of FSI.

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