Bursts in discontinuous Aeolian saltation.

Area of Science:

• Earth and Environmental Sciences
• Geophysics
• Fluid Dynamics

Background:

• Aeolian sediment transport is crucial for arid landscapes.
• Understanding the initiation of particle motion (saltation) is key.
• Turbulent wind fluctuations significantly influence particle entrainment.

Purpose of the Study:

• Investigate the dynamics of Aeolian particle transport near the saltation threshold.
• Characterize the discontinuous flux regime and its associated scaling laws.
• Explore the role of wind entrainment and feeding in sustaining saltation.

Main Methods:

• Wind tunnel experiments were conducted to observe particle transport.
• Measurements of wind fluctuations and time delays between particle bursts were recorded.
• A numerical model simulating saltation, including wind entrainment, was developed and validated.

Main Results:

• A regime of discontinuous particle flux, characterized by bursts, was identified near the saltation onset.
• Scaling laws were observed for the time delay between bursts and wind fluctuations at the fluid threshold (Shields number θc).
• The numerical model successfully reproduced the experimental observations, providing insights into the underlying mechanisms.

Conclusions:

• Discontinuous flux and burst dynamics are inherent to Aeolian saltation near the threshold.
• Wind entrainment driven by turbulent fluctuations plays a critical role in initiating and sustaining saltation.
• Sustaining discontinuous flux below the fluid threshold is achievable through particle feeding.