Power-Laws in Nonlinear Granular Chain under Gravity

TL;DR

This paper analytically derives and numerically verifies power-law relationships governing wave propagation in a gravitational granular chain with nonlinear contact forces, revealing how signals disperse with depth.

Contribution

It introduces analytical power-law formulas for various wave properties in a gravitational granular chain with nonlinear contact forces, supported by numerical validation.

Findings

Displacement signal follows a power-law with depth: h^{-1/4(1-1/p)}.

Velocity signal follows a power-law with depth: h^{-1/4(1/3+1/p)}.

Phase velocity scales as h^{1/2(1-1/p)}.

Abstract

The signal generated by a weak impulse propagates in an oscillatory way and dispersively in a gravitationally compacted granular chain. For the power-law type contact force, we show analytically that the type of dispersion follows power-laws in depth. The power-law for grain displacement signal is given by $h^{-1/4(1-1/p)}$ where $h$ and $p$ denote depth and the exponent of contact force, and the power-law for the grain velocity is $h^{-1/4({1/3}+1/p)}$. Other depth-dependent power-laws for oscillation frequency, wavelength, and period are given by combining above two and the phase velocity power-law $h^{1/2(1-1/p)}$. We verify above power-laws by comparing with the data obtained by numerical simulations.