Numerical modelling of flow structures over transverse aeolian dunes

Numerical flow models have been widely applied in engineering disciplines for many years. In the last few years, there has been a proliferation of the use of Computational Fluid Dynamics (CFD) in the fields of geomorphology and hydrology (see Bates and Lane, 1998). These models enable an improved simulation of important processes providing prediction fields that allow considerable insight into the spatial distribution of these processes. CFD modelling has offered a new methodology that is complementary to traditional field and laboratory approaches. Indeed, the models can provide details of the flow field that are often difficult to measure and offer controlled conditions in which certain aspects of the experimental set up can be varied rapidly. This paper applies a CFD model to flow over transverse desert dunes and describes the sensitivity of different elements of the flow field to variations in geomorphic parameters. The model used is capable of simulating the highly turbulent reverse flow vortex in the lee of the dune and so is able to provide an acceptable solution of the downwind distance to flow re-attachment given variations in dune height, windward slope length and aspect ratio.