title: Two-dimensional airflow modeling underpredicts the wind velocity over dunes.
abstract: We investigate the average turbulent wind field over a barchan dune by means of Computational Fluid Dynamics. We find that the fractional speed-up ratio of the wind velocity over the three-dimensional barchan shape differs from the one obtained from two-dimensional calculations of the airflow over the longitudinal cut along the dune's symmetry axis - that is, over the equivalent transverse dune of same size. This finding suggests that the modeling of the airflow over the central slice of barchan dunes is insufficient for the purpose of the quantitative description of barchan dune dynamics as three-dimensional flow effects cannot be neglected.
authors.affiliation: Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Britt
authors.initials: B
authors.lastname: Michelsen
authors.affiliation: Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Severin
authors.initials: S
authors.lastname: Strobl
authors.affiliation: Department of Geosciences, University of Cologne, Germany.
authors.forename: Eric J R
authors.initials: EJ
authors.lastname: Parteli
authors.affiliation: Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Pöschel