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This study presents an analysis of the abrasive effects of sediments from the bed of the Acre River, Brazil, on the wear of three different ferrous materials employed in the manufacture of impellers of centrifuge pumps used to catch raw water. In order to evaluate the abrasive wear and specific wear coefficient (k) as a function of sediment concentration, tests were conducted in samples of SAE 8620 steel, nodular cast iron and gray cast iron by using a rotary-ball abrasion meter. These tests employed abrasive slurry with concentration of 1, 2, 3, 5 and 10 g L-1 of sediments in distilled water. The volume of worn material as a function of the relative velocity of water flow in relation to the impeller blades was mathematically estimated. The experimental results showed that: i) The semi-angular and semi-rounded shapes of the sediments from the Acre River produced evidence of micro-grooving and plastic deformation in the three metallic alloys; ii) SAE 8620 steel showed higher resistance to abrasive wear than samples of gray and nodular cast iron; iii) the increase in the volume of worn material due to increment in sediment concentration and the relative velocity of the mixture (water + sediment) to the rotor pads.

The swimming ability of neotropical fish species is an important aspect for fish ladder designs. Especially in Latin America, where fish ladders are highly selective, fish strategies to negotiate the passage should be studied focusing on target species. This paper shows the swimming ability of three neotropical species (Leporinus reinhardti, Pimelodus maculatus and Prochilodus costatus), from São Francisco river basin. Respirometer was employed for data collection. Regarding the critical and prolonged speeds, L. reinhardti was the fastest among the three neotropical species in relative values (body length/ second). The performance of neotropical species was better when compared to critical and maximum prolonged speeds of fish species from temperate areas. Finally, regarding the experimental procedures, the optimization of swimming speed in respirometer is lower than the optimal processes obtained with free swimming in open channels.A capacidade natatória das espécies neotropicais de peixes é um importante aspecto a ser considerado em projetos de passagem para peixes. Especialmente na América Latina, aonde as passagens para peixes apresentam alta seletividade, estratégias para vencer barreiras de velocidade devem ser estudadas para espécies alvo. Este trabalho levantou a capacidade natatória de três espécies de peixes neotropicais (Leporinus reinhardti, Pimelodus maculatus e Prochilodus costatus) da bacia do rio São Francisco. Foi empregado o método forçado com uso de um em respirômetro. A comparação da velocidade entre as três espécies permitiu concluir que o L. reinhardti foi a espécie com maior velocidade crítica e velocidade prolongada em termos relativos (comprimentos/segundo). As espécies neotropicais foram mais rápidas, em termos relativos, do que as espécies de regiões temperadas, considerando velocidade crítica e máxima velocidade prolongada. Com relação aos procedimentos para determinação da capacidade natatória, verificou-se que a otimização da velocidade pelos peixes em respirômetro é inferior a desenvolvida em testes voluntários em canais abertos.

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Este é um artigo publicado em acesso aberto (Open Access) sob a licença Creative Commons Attribution, que permite uso, distribuição e reprodução em qualquer meio, sem restrições desde que o trabalho original seja corretamente citado. ABSTRACTSeveral fish transposition systems (MTP´s) have been employed to allow the fish upstream migration through river dams for spawning. The design of MTP´s of the type of vertical slot fishways requires not only the analysis of the pool hydraulic behavior to evaluate the velocity fields, the energy dissipation levels, and the Reynolds shear stress distributions, but also the study of biological characteristics of aquatic species impacted by the river dams. However, these parameters are not evaluated together, and some of them are valued at the average of the tank. This work deals with an analysis of the main hydraulic characteristics of a slot vertical fishway at two channel slopes, 6% and 12%. The hydraulic characteristic graphs obtained in this work show that a slope of 6% is preferable for the design of this kind of fishway, since the associated velocity magnitudes fits better to the ideal conditions for the safe fish passage. The slope of 12% creates restrictions in terms of the available area for fish passage due to power dissipation and shear stresses conditions.

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