A trans-scale simulation of aeolian sand flow – dune – dune field based on actual environmental wind field

Abstract

The present work employs a predictive model of fluctuating wind velocities constructed on the basis of long-term field observations to perform trans-scale simulations of aeolian sand flow, dune morphology and migration characteristics, and the overall evolution of dune fields. On the premise of comparing the simulated basic statistics of turbulent wind field and sand flow, and dune dynamic characteristics with experimental results to verify the reliability of our dune field model, the simulation results at different scales are compared with those of mean-flow based simulations to explore the effects of turbulent fluctuations. Analyses on sand transport rate of sand flow and average saltation length of sand particles indicated that turbulent fluctuations enhance the sand transport capacity of wind field, which promotes the initial morphological growth of dunes, dune migration and inter-dune interactions; and thus, more small size dunes with typical morphologic features are formed earlier within dune fields. The cumulative impacts of turbulence during long-term evolution accelerate the coarsening of dune field pattern, causing the dune number density to decline more rapidly, the dune height and inter-dune spacing to be larger in dune fields. Additionally, the turbulence effects enhanced with increasing wind velocities have more significant influences on small inertial particles with better following features. These findings contribute to insights into the effects of natural turbulent wind field on aeolian dune systems.