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Locomotion of self-excited vibrating and rotating objects in granular environments

Published version
Peer-reviewed

Change log

Abstract

jats:pMany reptiles, known as ‘sand swimmers’, adapt to their specific environments by vibrating or rotating their body. To understand these type of interactions of active objects with granular media, we study a simplified model of a self-excited spherical object (SO) immersed in the granular bed, using three-dimensional discrete element method (DEM) simulations. Modelling the vibration by an oscillatory motion, we simulate the longitudinal locomotion of the SO in three modes: transverse vibration, rotation around different axes, and a combination of both. We find that the mode of oscillation in y direction coupled with rotation around x-axis is optimal in the sense that the SO rises fastest, with periodic oscillations, in the z direction while remaining stable at the initial x position. We analyze the physical mechanisms governing the meandering up or down and show that the large oscillations are caused by an asynchronous changes between the directions of oscillation and rotation. We also observed that the SO’s rising rate is sensitive to three parameters: the oscillation amplitude, the oscillation frequency, f, and the rotation angular velocity, Ω. We report the following results. 1. When the frequencies of the rotation and transverse motion are synchronised, SO rises when Ω<0 and sinks when Ω>0; the average rising/sinking rate is proportional to |Ω|. 2. The rising rate increases linearly with the oscillation amplitude. 3. There exists a critical oscillation frequency, above and below which the rising mechanisms are different. Our study reveals the range of parameters that idealized ‘swimmers’ need to use to optimize performance in granular environments.</jats:p>

Description

Keywords

granular materials, LIGGGHTS, DEM simulations, rotation mode, vibration mode, bio-inspired robotics, locomotion, lizards

Journal Title

Applied Sciences (Switzerland)

Conference Name

Journal ISSN

2076-3417
2076-3417

Volume Title

11

Publisher

MDPI AG
Sponsorship
National Natural Science Foundation of China (11002162)
General Scientific Research Projects of NUDT (ZK16-03-01)