On the effect of two-direction seasonal flows on barchans and the origin of occluded dunes

Autor(es)

Assis, Willian R. ; Borges, Danilo S. ; Franklin, Erick M.

• Tipo de documento: Artigo Científico
• Fonte: Geomorphology; v. 467, p. 8-pg., 2024-11-06.

Resumo

We inquire into the morphodynamics of barchans under seasonal flows. For that, we carried out grain-scale numerical computations of a subaqueous barchan exposed to two-directional flows, and we varied the angle and frequency of oscillations. We show that when the frequency is lower than the inverse of the characteristic time for barchan formation, the dune adapts to the new flow direction and recovers the barchan shape while losing less grains than under one-directional flow. For higher frequencies, the dune has not enough time for adaptation and becomes more round while losing more grains. For both cases, we show, for the first time, the typical dynamics of grains (trajectories and forces). In particular, the round barchans are similar to the so-called occluded dunes observed on Mars, where seasons have very high frequencies compared to the dune timescale, different from Earth. Our results represent a possible explanation for that shape. (AU)

• Processo FAPESP: 18/14981-7 - Modelagem de escoamentos granulares densos: experimentos, simulações numéricas e análises de estabilidade
• Beneficiário: Erick de Moraes Franklin
• Modalidade de apoio: Auxílio à Pesquisa - Jovens Pesquisadores - Fase 2
• Processo FAPESP: 19/10239-7 - Instabilidades em leitos móveis: dinâmica granular e interação com o escoamento
• Beneficiário: Willian Righi Assis
• Modalidade de apoio: Bolsas no Brasil - Doutorado Direto
• Processo FAPESP: 22/01758-3 - Escoamento turbulento em meio granular denso: alterações na estrutura do escoamento
• Beneficiário: Danilo da Silva Borges
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado