Preprints
https://doi.org/10.5194/esurf-2022-55
https://doi.org/10.5194/esurf-2022-55
 
01 Nov 2022
01 Nov 2022
Status: this preprint is currently under review for the journal ESurf.

The probabilistic nature of dune collisions in 2D

Paul A. Jarvis1,2, Clement Narteau3, Olivier Rozier3, and Nathalie M. Vriend4,1,5 Paul A. Jarvis et al.
  • 1Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforece Road, Cambridge, CB3 0WA, UK
  • 2GNS Science, 1 Fairway Drive, Lower Hutt, 5011, New Zealand
  • 3Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, 1 Rue Jussieu, Paris, 75005, France
  • 4BP Institute, University of Cambridge, Madingley Road, Cambridge, CB3 0EZ, UK
  • 5Department of Earth Sciences, University of Cambridge, Madingley Road, Cambridge, CB3 0EZ, UK

Abstract. Dunes are bedforms of different size and shape, appearing throughout aeolian, subaqueous and extra-terrestrial 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 downstream- or upstream-dominant coalescence (merging of dunes) or ejection, where dunes exchange mass before separating. 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 r and can be described by a narrow sigmoidal function centred on r = 1/2. 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.

Paul A. Jarvis et al.

Status: open (until 25 Dec 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on esurf-2022-55', Dominic Robson, 04 Dec 2022 reply

Paul A. Jarvis et al.

Paul A. Jarvis et al.

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Short summary
Sand dune migration velocity is inversely proportional to dune size. Consequently, smaller, faster dunes can collide with larger, slower, downstream dunes. Such collisions can result in either coalescence or ejection, whereby the dunes exchange mass but remain separate. Our numerical simulations show that the outcome depends probabilistically on the dune size ratio, which we describe through an empirical function. Our numerical predictions compare favourably against experimental observations.