Density waves and $1/f$ density fluctuations in granular flow

TL;DR

This study uses a lattice-gas automaton model to simulate granular flow in a narrow pipe, revealing that density waves propagate with specific shapes and velocities, and that their distribution results in $1/f^{eta}$ noise in density fluctuations.

Contribution

It demonstrates how energy dissipation, average density, and wall roughness influence density wave behavior and $1/f$ noise in granular flow simulations.

Findings

Density waves propagate with well-defined shapes and velocities.

Density fluctuations exhibit $1/f^{eta}$ noise spectra.

Key parameters affecting phenomena are energy dissipation, density, and wall roughness.

Abstract

We simulate the granular flow in a narrow pipe with a lattice-gas automaton model. We find that the density in the system is characterized by two features. One is that spontaneous density waves propagate through the system with well-defined shapes and velocities. The other is that density waves are so distributed to make the power spectra of density fluctuations as $1/f^{\alpha}$ noise. Three important parameters make these features observable and they are energy dissipation, average density and the rougness of the pipe walls.