Reciprocal swimming in granular media: the role of jamming and swimmer inertia

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Hauptverfasser: Nazemi, Amir, Xiao, Hongyi
Format: Preprint
Veröffentlicht: 2025
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author Nazemi, Amir
Xiao, Hongyi
author_facet Nazemi, Amir
Xiao, Hongyi
contents We use particle simulations to reveal two distinct propulsion mechanisms for a scallop-like swimmer to locomote itself in granular media by reciprocally flapping its wings. Based on the discrete element method, we examine the kinematics and contact forces of particles near the swimmer to identify jamming effects induced by the swimmer in a frictional granular medium, which are less intense during the opening stroke than the closing. This broken symmetry is quantified by the difference in the number of strong particle contact forces formed during opening and closing, which shows a linear relation with the swimmer's net displacement across various swimmer and medium configurations, all favoring the opening stroke. We identify a secondary propulsion mechanism in a dynamic regime with significant swimmer inertia, as the flapping period approaches the coasting time for a moving swimmer to come to rest under the medium resistance. In this case, the swimmer's net displacement is correlated to the ratio between these two time scales, and the swimming direction favors the closing stroke due to the smaller medium resistance as the swimmer coasts with closed wings.
format Preprint
id arxiv_https___arxiv_org_abs_2510_22081
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Reciprocal swimming in granular media: the role of jamming and swimmer inertia
Nazemi, Amir
Xiao, Hongyi
Soft Condensed Matter
Fluid Dynamics
We use particle simulations to reveal two distinct propulsion mechanisms for a scallop-like swimmer to locomote itself in granular media by reciprocally flapping its wings. Based on the discrete element method, we examine the kinematics and contact forces of particles near the swimmer to identify jamming effects induced by the swimmer in a frictional granular medium, which are less intense during the opening stroke than the closing. This broken symmetry is quantified by the difference in the number of strong particle contact forces formed during opening and closing, which shows a linear relation with the swimmer's net displacement across various swimmer and medium configurations, all favoring the opening stroke. We identify a secondary propulsion mechanism in a dynamic regime with significant swimmer inertia, as the flapping period approaches the coasting time for a moving swimmer to come to rest under the medium resistance. In this case, the swimmer's net displacement is correlated to the ratio between these two time scales, and the swimming direction favors the closing stroke due to the smaller medium resistance as the swimmer coasts with closed wings.
title Reciprocal swimming in granular media: the role of jamming and swimmer inertia
topic Soft Condensed Matter
Fluid Dynamics
url https://arxiv.org/abs/2510.22081