Barchans Interacting With Dune-Size Obstacles: Details of the Fluid Flow and Motion of Grains

Autor(es)

Lima, N. C. ; Assis, W. R. ; Borges, D. S. ; Franklin, E. M.

• Tipo de documento: Artigo Científico
• Fonte: JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE; v. 130, n. 6, p. 17-pg., 2025-06-01.

Resumo

We investigate details of the interaction of subaqueous barchans with dune-size obstacles by carrying out numerical simulations where the fluid is solved at the grain scale and the motions of individual grains are computed at all time steps. With the outputs, we analyze the disturbances of the fluid flow, the trajectories of grains, and the resultant force on each grain, the latter being unfeasible from experiments and field measurements. We show that in some cases particles pass over the obstacle, while in others they completely circumvent it (without touching it), or are even blocked. For the circumvention and blocking cases, which we call bypass and trapped, respectively, we show the existence of a strong vortex between the lee face of the dune and the obstacle. This vortex results from the interactions of recirculation regions and horseshoe vortices, and has enough strength to deviate the main flow and carry grains around the obstacle in those cases. Our results shed light on the reasons for passing over, circumventing, and blocking, and contribute to our understanding of dunes in the presence of large obstacles such as hills, crater rims, and human constructions. (AU)

• 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
• 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: 19/20888-2 - Simulações CFD-DEM em leitos fluidizados
• Beneficiário: Nicolao Cerqueira Lima
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado