SKM 2023 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 7: Granular Matter and Contact Dynamics

DY 7.4: Vortrag

Montag, 27. März 2023, 10:45–11:00, ZEU 148

Shear jamming and free surface deformation enable reciprocal swimming in granular materials — •Hongyi Xiao, Achim Sack, and Thorsten Pöschel — Institute for Multiscale Simulations, Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstraße 3, 91058 Erlangen, Germany

Swimming with reciprocal motion is desirable due to its simplicity, but it is prohibited in Newtonian fluids at low Reynolds number as stated by the scallop theorem. Such a constraint can be broken in fluids with complex rheology. In this study, we show that propulsion generation with reciprocal motion in granular materials is enabled by a prolonged hysteresis in the material response, which originates from a combination of jamming-induced material rigidity and plastic deformation of the free surface. Using both lab experiments and discrete element method simulations, a reciprocal swimmer mimicking a scallop was constructed and buried in a tank of polydisperse granular particles. The swimmer consists of two wings that open and close with geometrical and temporal symmetry. The resistive force, the swimmer's displacement, and the deformation of the free granular surface were measured. Results indicate that net propulsion force is generated when the swimmer is tethered, and net displacement is generated when the swimmer is released. Small amplitude oscillatory experiments confirm the existence of an elastic regime at small strains, and free surface deformation measurement reveals its influence at large strains. Furthermore, a secondary symmetry breaking mechanism due to a cooperative effect of the wings is also identified.