Anomalous Scaling of Aeolian Sand Transport Reveals Coupling to Bed Rheology

TL;DR

This paper investigates the complex interactions in windblown sand transport, revealing a new scaling law and steady state through simulations and modeling, with implications for planetary and environmental sciences.

Contribution

It introduces a coupled grain-bed collision and granular creep model that explains anomalous sand transport scaling and predicts a new steady transport state.

Findings

Identifies a third-root scaling law in sand transport.

Develops a minimal saltation model that predicts observed scaling.

Confirms a new steady transport state via simulations.

Abstract

Predicting transport rates of windblown sand is a central problem in aeolian research, with implications for climate, environmental, and planetary sciences. Though studied since the 1930s, the underlying many-body dynamics is still incompletely understood, as underscored by the recent empirical discovery of an unexpected third-root scaling in the particle-fluid density ratio. Here, by means of grain-scale simulations and analytical modeling, we elucidate how a complex coupling between grain-bed collisions and granular creep within the sand bed yields a dilatancy-enhanced bed erodibility. Our minimal saltation model robustly predicts both the observed scaling and a new undersaturated steady transport state that we confirm by simulations for rarefied atmospheres.