Unification of Aeolian and Fluvial Sediment Transport Rate from Granular Physics

TL;DR

This paper unifies the understanding of sediment transport rates in air and water by linking the nonlinear and linear dependencies on shear stress to the dissipation mechanisms of particle kinetic energy, supported by simulations and a derived scaling law.

Contribution

It introduces a unified framework explaining sediment transport rate dependencies in air and water based on energy dissipation mechanisms, supported by simulations and a new scaling law.

Findings

Transport rate depends on dissipation mechanisms of particle energy.

Derived scaling law $Q\sim\tau^2$ matches experimental data.

Unified explanation for linear and nonlinear dependencies in different media.

Abstract

One of the physically least understood characteristics of geophysical transport of sediments along sediment surfaces is the well known experimental observation that the sediment transport rate $Q$ is linearly dependent on the fluid shear stress $\tau$ applied onto the surface in air, but is nonlinearly dependent on $\tau$ in water. Using transport simulations for a wide range of driving conditions, we show that the scaling depends on the manner in which the kinetic fluctuation energy of transported particles is dissipated: via predominantly fluid drag and quasistatic contacts (linear) versus fluid drag and quasistatic and collisional contacts (nonlinear). We use this finding to derive a scaling law (asymptotically $Q\sim\tau^2$) in simultaneous agreement with measurements in water and air streams.