Midair collisions enhance saltation

TL;DR

This study investigates the impact of midair collisions on saltation in Aeolian particle transport, revealing that such collisions significantly increase particle flux, especially at certain restitution coefficients and wind speeds.

Contribution

It demonstrates that midair collisions enhance saltation flux and identifies the optimal restitution coefficient for maximum flux, a novel insight into Aeolian processes.

Findings

Midair collisions substantially increase saltation flux.

Flux peaks at an intermediate restitution coefficient (~0.7).

The effect varies with wind speed and restitution coefficient.

Abstract

Here we address the old question in Aeolian particle transport about the role of midair collisions. We find that, surprisingly, these collisions do enhance the overall flux substantially. The effect depends strongly on restitution coefficient and wind speed. We can explain this observation as a consequence of a soft-bed of grains which floats above the ground and reflects the highest flying particles. We make the unexpected observation that the flux is maximized at an intermediate restitution coefficient of about 0.7, which is comparable to values experimentally measured for collisions between sand grains.