Discrete Particle Model for Analyzing Bedform Development

A discrete element model is used to simulate the emergence and evolution in time of wind ripples with the use of simple rules for the motion of individual sediment particles. It is shown, by analyzing the probabilities for the particles to be entrained and deposited over the bed implied by the selected rules, that the same model can be used to simulate the development of underwater bedforms. The results of the model show that the particle-transport processes implied by the simple rules used in the model can represent many different complex aspects of the physics of bedforms. The results of the model are compared with experimental results on underwater ripples obtained by the authors, and a surprisingly good agreement is found in terms of the main dynamical properties of the bedforms, such as growth rate of the amplitude, evolution of the steepness, growth saturation, and bedform celerity. Even though the simulated bedforms do not reproduce the exact geometry of their physical counterparts, the richness of the strongly nonlinear processes that this simple model is able to simulate makes this kind of approach useful to explain many of the observed features of underwater bedforms, which are otherwise very difficult to address theoretically.