Temperature-pressure scaling for air-fluidized grains on approaches to Point J

TL;DR

This study investigates the jamming transition in air-fluidized beads by examining pressure, packing, and kinetic energy, revealing a unique temperature-pressure scaling behavior distinct from thermal systems.

Contribution

It introduces a novel experimental approach to study jamming in granular media and derives an equation of state with a new scaling form for relaxation time.

Findings

Relaxation time diverges as effective temperature to pressure ratio approaches zero.

Data collapse achieved through dimensionless scaling of time and temperature.

The scaling form differs from that of thermal hard-sphere systems.

Abstract

We present experiments on a monolayer of air-fluidized beads in which a jamming transition is approached by increasing pressure, increasing packing fraction, and decreasing kinetic energy. This is accomplished, along with a noninvasive measurement of pressure, by tilting the system and examining behavior vs depth. We construct an equation of state and analyze relaxation time vs effective temperature. By making time and effective temperature dimensionless using factors of pressure, bead size, and bead mass, we obtain a good collapse of the data but to a functional form that differs from that of thermal hard-sphere systems. The relaxation time appears to diverge only as the effective temperature to pressure ratio goes to zero.