Phys. Rev. Lett. 62, 2825–2828 (1989)Pattern formation in flowing sandReceived 23 November 1988; published in the issue dated 12 June 1989 Using digital subtraction radiography, we study the basic modes of a granular material (here sand) flowing through a flat hopper. These modes take the form of density waves whose formation and propagation is controlled by several parameters, including the mass flow rate M and the hopper angle θ. We consider the effect of roughness on pattern formation in this system using mixtures of smooth and faceted sand and show the existence of a bifurcation at a mass fraction of faceted sand X≊0.2. Propagating patterns form in faceted sand but not in smooth sand of the same size. © 1989 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevLett.62.2825
DOI:
10.1103/PhysRevLett.62.2825
PACS:
47.35.+i, 47.50.+d, 62.90.+k
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