Competitive dynamics of two erosion patterns around a cylinder

We investigate experimentally the local erosion of a granular bed near a fixed vertical cylinder that emerges from the bed. The onset of erosion arising at the base of the cylinder and usually ascribed to the wrapping horseshoe vortex is determined and rationalized by a flow contraction effect. We report a new erosion pattern visible downstream of the cylinder that consists of two side-by-side elongated holes. This pattern is observed for flow regimes close to the horseshoe scour onset, whose growth usually inhibits its spatiotemporal development.Comment: 6 pages, 6 figure

Experimental investigation of tsunami waves generated by granular collapse into water

The generation of a tsunami wave by an aerial landslide is investigated through model laboratory experiments. We examine the collapse of an initially dry column of grains into a shallow water layer and the subsequent generation of waves. The experiments show that the collective entry of the granular material into water governs the wave generation process. We observe that the amplitude of the wave relative to the water height scales linearly with the Froude number based on the horizontal velocity of the moving granular front relative to the wave velocity. For all the different parameters considered here, the aspect ratio and the volume of the column, the diameter and density of the grains, and the height of the water, the granular collapse acts like a moving piston displacing the water. We also highlight that the density of the falling grains has a negligible influence on the wave amplitude, which suggests that the volume of grains entering the water is the relevant parameter in the wave generation.Comment: 23 pages, 16 figure

Competitive dynamics of two erosion patterns around a cylinder

We investigate experimentally the local erosion of a granular bed near a fixed vertical cylinder that emerges from the bed. The onset of erosion arising at the base of the cylinder and usually ascribed to the wrapping horseshoe vortex is determined and rationalized by a flow contraction effect. We report a new erosion pattern visible downstream of the cylinder that consists of two side-by-side elongated holes. This pattern is observed for flow regimes close to the horseshoe scour onset, whose growth usually inhibits its spatiotemporal development

Restauração do pavilhão, cúpula metálica e luneta equatorial de 32 cm: conjunto arquitetônico do Museu de Astronomia e Ciências Afins (MAST)

MAST is a science and technology museum located in the grounds and architectural\ud complex belonging to the former Observatório Nacional in Rio de Janeiro. This complex, concluded\ud in 1921, comprises of 16 buildings, and was listed by the Artistic and Historic National (1986)\ud and State (1987) Heritage. This complex features three pavilions sheltering the equatorial\ud telescopes, typical examples of Architecture and Engineering buildings for Astronomic purposes.\ud Two of these pavilions, all of which are under the care of MAST, shelter the 21 cm and 32 cm\ud telescopes, plus a third, part of the National Observatory, which houses the 46 cm equatorial\ud telescope. The present study is the result of the work undertaken by MAST to preserve and restore\ud the historical buildings under its responsibility. Thanks to a partnership set up with the Vitae\ud Foundation, it has been possible to develop restoration work covering all aspects of the pavilions\ud (moving metal dome, building, scientific instrument), as well as the areas museography, with a\ud view to informing visitors about the restoration work undertaken. The project, based on the\ud historical research on the complex, was carried out by a multidisciplinary team over two years.\ud Each stage of the work was comprehensively photographed, including the intervention project\ud design, which was based on architectural surveys and the diagnosis of the complexs state of\ud repair, plus the restoration per se. This is a groundbreaking initiative in Latin America and will\ud serve as an example for future actions to be taken on historical buildings, especially those built\ud for scientific and technological purposes