Wind tunnel simulation of the aeolian erosion on the leeward side of barchan dunes and its implications for the spatial distribution patterns of barchan dunes

Abstract

The interactions between wind flow and sand transport on the leeward side of dunes are complex due to highly turbulent fluctuations. Most models of turbulent flow on the individual barchan dunes have recognized the flow structure of recirculation cell and shear stress within the Inner Boundary Layer (IBL) on the leeward side, however these models neglected the processes of aeolian erosion caused by the recovering flow and reversed flow. Here, we investigated the airflow and aeolian erosion processes of an erodible surface on the leeward side of a barchan dune in a scaled wind tunnel simulation. Results show that the recovering flow triggered the wind erosion on the leeward side of barchan dunes through the unsaturated flux. The length of the wind erosion zone ranged from 4.5 to ~16H (H is the dune height). Under the condition of abundant sand supply, the length of wind erosion zone decreases slightly. However, abundant sand supply has notably weakened the wind erosion rate, and individual barchan dunes link into sinuous-crested ridges. As confirmed by field observations, this study provides empirical evidence for aeolian erosion on the leeward side of barchan dunes and suggests that airflow recovery length and sand supply collectively determine the spatial distribution patterns of barchan dunes on Earth.