Fundamentals of Aeolian Sediment Transport: Airflow Over Dunes

Airflow dynamics over dunes differ significantly from those over flat terrain due to topographically generated pressure fields that cause deviations in flow behavior (e.g., streamline compression, expansion and/or curvature, flow separation and/or reversal). Recent research using ultrasonic anemometry, modeling of computational fluid dynamics (CFD), wind tunnel simulations, and detailed field experiments have enhanced our understanding of boundary layer flow over dunes and, thus, advanced recent efforts to model the interactions between dune geomorphology, airflow dynamics, and sand transport. This chapter reviews principally the fundamentals of airflow over and in the lee of transverse dunes and discusses several key advances and limitations in measurement and modeling of flow dynamics. Although progress in our understanding has been made mostly via study of transverse desert dunes, due to their relatively simple shape and surface roughness characteristics (i.e., no vegetation), research advances from other dune settings (e.g., coastal foredunes) are also reviewed briefly. Though covered more extensively in other chapters, implications for sediment transport and dune morphodynamics are also discussed. Areas for further research are identified based on gaps in knowledge on the implications of flow dynamics for mesoscale (i.e., landform to landscape scale) dune sediment budgets, migration and morphological evolution.