Aeolian sans ripples: experimental study of saturated states

TL;DR

This experimental study investigates aeolian sand ripples, revealing linear relationships between wind velocity and ripple characteristics, and demonstrating stable saturation states that challenge existing models.

Contribution

It provides new experimental evidence of ripple saturation and nonlinear stable solutions, contrasting with prior theoretical models.

Findings

Ripple wavelengths and speed are linearly related to wind velocity.

Stable saturated ripple states exist with finite amplitude.

Results challenge existing theoretical models of aeolian ripples.

Abstract

We report an experimental investigation of aeolian sand ripples, performed both in a wind tunnel and on stoss slopes of dunes. Starting from a flat bed, we can identify three regimes: appearance of an initial wavelength, coarsening of the pattern and finally saturation of the ripples. We show that both initial and final wavelengths, as well as the propagative speed of the ripples, are linear functions of the wind velocity. Investigating the evolution of an initially corrugated bed, we exhibit non-linear stable solutions for a finite range of wavelengths, which demonstrates the existence of a saturation in amplitude. These results contradict most of the models.