An experimental and numerical study of the aeolian erosion of isolated and successive piles

Open storage yards at industrial sites usually comprise several piles of granular materials, representing a particulate matter source that may significantly deteriorate air quality. The aeolian erosion of stockpiles is affected by changes in airflow patterns due to the pile shape and the presence of nearby piles or buildings. The aim of this study was to analyse the impact of wind erosion of successive parallel stockpiles on flow behaviour and particle emissions. A wind tunnel experiment was conducted in six configurations: one isolated pile and two successive piles separated by gaps of 0.9h and 1.8h (h is the pile height) oriented to 60 degrees and 90 degrees with respect to the main wind flow direction. The particles in the piles had a bimodal particle size distribution consisting of sand that was erodible (white) and non-erodible (black) in the investigated velocity range. The contrasting colours enabled the visualisation of the non-erodible sand accumulation. The mean field of the wall shear stress distribution and flow pathlines predicted by numerical simulation were associated with the experimental erosion patterns. The emitted mass was experimentally quantified as the difference between the initial and final stockpile weights. Downstream pile had a large impact on the aeolian erosion as it was highly eroded as a result of the impact of the particles emitted from the upstream pile. The emissions of the two consecutive stockpiles were greater than twice the emissions from an isolated stockpile for both orientations. Additionally, emissions were lower for configurations in which the piles were perpendicular.