Large eddy simulation of dune evolution by wind erosion, sand transport and deposition

International audienceSand dune deformation is a dynamic process resulting from a complex interplay between the atmospheric boundary layer, aeolian particle transport and sand erosion. This work undertakes these problems by conducting three-dimensional numerical simulations of solid particle transport over a deformable sand dune.A turbulent boundary layer flow is resolved by Large-eddy simulations (LES). An immersed boundary method (IBM) is used to take into account moving and deformable boundaries. Lagrangian particle tracking is applied for sand transported by the incoming turbulent flow. Particle entrainment, particle-surfaceinteractions and particle deposition are taken into account by a physical wind erosion model,based on the forces acting on individual particles in the flow or within the sand bed according to Huang et al. (2019). The advantage of this model is that it relies on instantaneous quantities provided by the LES. It therefore avoids the use of averaged and global flow characteristics such as the friction velocity. An avalanche model is also introduced when the local slope exceeds the angle of repose.Simulations of particle transport over a deformable sinusoidal dune are carried out. The simulated dune shapes are compared with the experimental results obtained by Ferreira et al. (2012). Good agreement is achieved. A consistent small-scale tool for predicting particle transport and wind erosion around a deforming surface represented by a dune is therefore presented and validated in this work