Spatial characteristics of wind-sand flow development under natural wind

The spatial characteristics of wind-sand flow development are important for the morphological analysis of sand dunes (especially barchan dunes) used for curbing desertification projects. However, in previous studies, results were mostly obtained under the premise of a stable wind field. In this study, natural unsteady wind is accounted for, and the two-dimensional turbulent flow equilibrium differential equation (the N–S equation) is solved by large-eddy simulation method. On the premise that the characteristics of the simulated flow field are consistent with those of natural wind field, a point force model is used to calculate the trajectory of a large number of dust particles. The analysis focuses on the correlation between the development distance of the wind-sand flow, the turbulence characteristics of the wind field, and the particle size of sand. The results show that the saturation length of the unsteady incoming flow is generally shorter than that of the steady incoming flow (The turbulence intensity is equal to 0). Moreover, the overshoot phenomenon is not obvious when the particle size is small, the maximum value of the sand transport rate is generally smaller than that in stable inflow environment, and the position is more forward as the particle size increases. In addition, the saturation length decreases with an increase in turbulence intensity, and the turbulence intensity is different for the sand transport rate after space development is stable. The sand transport rate is not only delayed in time (< 2 s) but also delayed in space (~ 2.4 m). Graphical Abstract