In the last decades, different scientists have explored a variety of CA
approach in order to model dune features in arid desert on Earth. In
all cases, despite a stochastic ingredient, the trajectory of an
elementary volume of grains does not dissociate transport, erosion and
deposition
processes. In addition, there is no treatment of aerodynamics effect.
In our CA model for sediment transport, individual physical processes
such as erosion, deposition and transport are implemented by nearest
neighbor interactions and a time-dependent stochastic process.
Simultaneously, a lattice gas CA model is used to compute the flow and
quantify the bed shear stress on the topography. Then, the dependence
of the erosion rate on the bed shear stress as well as the rebounds
dynamics of fluid particles on sedimentary cells ensure permanent
feedback mechanisms between flow and topography (see Narteau et al. 2009).
Barchan
dunes are isolated structures with horns extending downwind on both sides of a
sand pile characterized by a slip face and a windward face. From outputs of the
model, we study the mechanics of an individual barchan dune under a variety
of wind conditions and the dynamic of a population of dunes in response to
variation in sand availability. To facilitate our work, we
develop different numerical tools that allow calculating the evolution of the frequency-size
relationship as well as the grain flux perpendicularly to the flow during our
computations.
Dunes in arid desert on Earth
Dunes in the model (click on the pictures for movies)
Formation and evolution of an individual barchan dune
Transverse
Dunes
Formation and evolution of a population of barchan dunes