The probabilistic nature of dune collisions in 2D

Jarvis, Paul A.; Narteau, Clement; Rozier, Olivier; Vriend, Nathalie M.

Dunes are bedforms of different size and shape, appearing throughout aeolian, subaqueous and extraterrestrial environments. Collisions between dunes drive dune field evolution, and are a direct result of interacting dunes of different heights, travelling at different speeds. We perform 2D cellular automaton simulations of collisions between dune pairs migrating in a steady flow. Modelled collisions can result in either ejection, where dunes exchange mass before separating, or downstream- or upstream-dominant coalescence (merging of dunes). For each of these three elementary types of interaction, we identify the mass exchange mechanism and the distinctive intermediate morphologies. Surprisingly, we show that the collision outcome depends probabilistically on the initial dune area ratio inline-formular and can be described by a narrow sigmoidal function centred on inline-formula M2inlinescrollmathml r = normal 1 / normal 2 38pt14ptsvg-formulamathimgd83d08a391b344b223a48aab33ec74ec esurf-11-803-2023-ie00001.svg38pt14ptesurf-11-803-2023-ie00001.png . Finally, we compare our simulations with laboratory experiments of dune collisions, finding good agreement concerning the intermediate morphology and the collision outcome. Our results can motivate further observational or experimental studies that validate our probabilistic collision predictions and fully determine the controls on the coalescence–ejection transition.



Jarvis, Paul A. / Narteau, Clement / Rozier, Olivier / et al: The probabilistic nature of dune collisions in 2D. 2023. Copernicus Publications.


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