The Scale Characteristics and Formation Mechanism of Aeolian Sand Streamers Based on Large Eddy Simulation

Abstract

Aeolian sand transport near the surface in the field often occurs in the form of sand streamers, which is very important to understand in‐depth the physics of aeolian transport and accurately predict the sand transport rate. In this paper, sand streamers were successfully reproduced by combining the Lagrangian trajectory simulation of particles with large eddy simulation of turbulence. The simulated sand streamers are hill‐like. Their characteristic scales are extracted by the two‐point correlation of sand concentration. It is found that sand streamers corresponding to the correlation threshold of Rcpcp=0.4 are 2.0–4.5 m long and 0.3–0.4 m wide, while 30–100 m long and 1.2–2.4 m wide for Rcpcp=0.05, which are substantially consistent with the existing field observation results and increases with particle size. Conditional averaging method provided an ensemble‐mean visualization of flow structures that are responsible for the formation of streamers. It is found that sand streamers on a flat and erodible surface exist in the near‐surface wake area of large/very large scale turbulent motions (LSMs/VLSMs), indicating that sand streamers are the footprint of LSMs/VLSMs. Moreover, the characteristic scales of sand streamers will be affected by the splashing process of sand saltation. On a nonerodible surface, sand streamers trailing from upstream sandy surface become narrow though it can propagate downstream for a long distance.

Modulation of turbulence by saltating particles on erodible bed surface

“…(2013) and Wang et al. (2019) to involve the splashing process in the simulations. Briefly, the probability that a particle rebounds is approximated by a negative exponential function of where is the particle impacting velocity and m s is an empirical constant.…”

Attached eddy-like particle clustering in a turbulent boundary layer under net sedimentation conditions

“…One classic example is the aeolian streamer, which describes the strip-like concentration of wind-blown sand grains near the surface of a desert (Baas & Sherman 2005; Wang et al. 2019 a ). Several approaches, including the radial distribution function, the box-counting method and Voronoï analysis, have been devised for rigorous detection and quantification of particle clusters.…”

The Influence of Surface Stress Fluctuation on Saltation Sand Transport Around Threshold

“…Dupont et al (2013) visualized for the first time the blowing sand structures (known as sand streamer) and the saltation intermittency based on the data obtained from their two-way coupling simulations. Wang et al (2019) further discussed the effect of large-scale and very large scale motions (LSMs/VLSMs) on sand streamers within a quiet large simlulation domain. Li et al (2014) simulated aeolian sand transport using a coupled LES-DEM (discrete element method) code.…”