The probabilistic nature of dune collisions in 2D
<p>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 c...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2023-08-01
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| Series: | Earth Surface Dynamics |
| Online Access: | https://esurf.copernicus.org/articles/11/803/2023/esurf-11-803-2023.pdf |
| Summary: | <p>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 <span class="inline-formula"><i>r</i></span> and can be described by a narrow sigmoidal function centred on <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M2" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>r</mi><mo>=</mo><mn mathvariant="normal">1</mn><mo>/</mo><mn mathvariant="normal">2</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="38pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="d83d08a391b344b223a48aab33ec74ec"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="esurf-11-803-2023-ie00001.svg" width="38pt" height="14pt" src="esurf-11-803-2023-ie00001.png"/></svg:svg></span></span>. 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.</p> |
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| ISSN: | 2196-6311 2196-632X |