Period tripling causes rotating spirals in agitated wet granular layers

TL;DR

This study experimentally investigates pattern formation in wet granular layers under vertical agitation, revealing that period tripling leads to rotating three-armed spirals, a behavior distinct from dry granular systems.

Contribution

It demonstrates that period tripling causes rotating spirals in wet granular layers, highlighting a novel pattern formation mechanism in wet granular matter.

Findings

Rotating three-armed spirals are observed as dominant patterns.

The spirals are linked to period tripling in the system.

Chirality of patterns matches spiral rotation direction.

Abstract

Pattern formation of a thin layer of vertically agitated wet granular matter is investigated experimentally. Rotating spirals with three arms, which correspond to the kinks between regions with different colliding phases, are the dominating pattern. This preferred number of arms corresponds to period tripling of the agitated granular layer, unlike predominantly subharmonic Faraday crispations in dry granular matter. The chirality of the spatiotemporal pattern corresponds to the rotation direction of the spirals.