A Numerical Research on the Relationship between Aeolian Sand Ripples and the Sand Flux

Abstract

Theoretically, the sand flux will not change after the wind-driven sand particle transport reaches the saturated state. However, it has been found in many wind-tunnel experiments that the sand flux will gradually decrease with time in long-term particle transport duration and will eventually reach a new stable state. In this work, we used numerical simulations to study the source of this kind of decrease and found it is caused by the sand ripple on the bed surface. The ripple index showed a strong correlation to the sand flux, and it decreased during the initial stage of the ripple formation. With a simplified theoretical model, we found the linear relationship between the Shields number and the particle transport load holds. However, the slope of this relationship and the dynamic threshold of particle entrainment decreased with the ripple index. As the sand flux scales linearly with the particle transport load, we finally derived an expression that describes how the sand flux on the ripple bedform varies with the wind strength. From this expression, we found the sand flux increases with ripple index, and it was easier to be influenced by the ripple bed form in small wind strength.

Mid‐Air Collisions Control the Wavelength of Aeolian Sand Ripples

“…The numerical results data used in the study are available at Zenodo via https://doi.org/10.5281/zenodo.7467377 (Huo et al, 2022). The detailed description of the numerical model can be found in (Huo et al, 2021).…”