Computational Fluid Dynamics Simulation of Wind Over Sand Dunes

Active sand dunes complexes are constantly reshaped by the wind. However, in coastal, vegetated dunes, plants act to anchor slopes with their roots and present a physical barrier to wind flow at the surface and sand movement.  On surfaces that have been stabilized by vegetation, the plants can die out, leaving unprotected bare sand patches.  These patches may erode developing into blowouts. The interaction of the wind with these blowouts determines the early dynamics of sand dune growth and migration and by extension has a large impact on the coastline.

To study wind flow in bare sand patches we used the computational fluid dynamics (CFD) software OpenFOAM. We started with a simple 2D geometry, reflecting a simplified dune surface including bare patches of various sizes.  The flow was initially simulated using a RAS model. Within OpenFOAM, the mesh geometry, inlet wind speed, and boundary conditions were set. The inlet wind speed was set to vary logarithmically with height above the surface, and the inlet wind speed at one meter was varied between simulations.  The simulation results can be used to predict the shear stress along the surface of the dune, which determines the capacity for sand transport.