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Estudo da fluidodinâmica em leito fixo utilizando-se métodos numéricos de solução: escoamento monofásico de ar
(Universidade Federal de São Carlos, 2006-03-09) Béttega, Rodrigo; Corrêa, Ronaldo Guimarães
Studies accomplished in the structure of tubular fixed beds proved that the porosity in these systems presents an oscillatory behavior along the radial direction. The non-uniformity of the porosity generates a behavior of the velocity profile, inside the bed, characterized by oscillations in the central region and a peak of larger width in the region close to the wall. This velocity profile determines the residence time of the reactants, for example, and presents a strong influence in the heat and mass transfer coefficients of these systems. In spite of the progress obtained in that subject, it is still difficult to obtain the measure of flow velocity inside the bed without causing disturbances in its structure. Due to this restriction, indirect forms of experimental measure of the velocity distribution in these systems have been proposed to evaluate the fluid dynamics inside the bed. The most common way to obtain, experimentally, the velocity distribution inside the bed is to measure it outside the bed, at a certain distance from its exit, and then infer it inside the bed by considering that the flow measured at this point maintains the fluid dynamics characteristics at the interface. Looking for an alternative way to infer the velocity profile inside the fixed bed, this work proposes a measure of the change in flow characteristics from the exit of the fixed bed to the point of experimental measurement. The measure proposed before takes into account the change in the radial mean velocity evaluated over an area close to the central part of the flow. This measure is based on simulated results accomplished between these two points, located outside the fixed bed, from an appropriated boundary condition at the interface. This boundary condition at interface is the result of other simulations performed inside the fixed bed, from a convenient model proposed for this region. Both simulations were accomplished by using a simulator developed in FORTRAN language, based on a CFD numeric technique for outside and a standard finite difference method for inside the fixed bed. The validity of the proposed procedure was verified by comparing the velocity distribution simulated at a position pointed out in an experimental measurement of the velocity distribution obtained in the literature, and with similar operational conditions. By doing this validation, it was established a relationship between the change in flow characteristics and the axial position of measurement. As a result, it was possible to infer how much of the flow characteristics in the interface are observed from the position chose for measurement along the axial direction of the flow. Better results were observed in systems with a high dimensionless D/Dp relation and low values of Reynolds number for the flow simulations accomplished in the exit area of the bed. Deviations from experimental data, varying between 2,97% and 30,23%, were verified for different operational conditions of the system. Through the central velocity simulation along in the empty tube axial position, were possible to map the empty tube influences on the flow in the fixed bed exit area, evaluating the difference of that central medium velocity with the calculated for the bed exit.
Influência de práticas de manejo de solo sobre os macroinvertebrados aquáticos de córregos: ênfase para o cultivo de cana-de-açucar em áreas adjacentes
(Universidade Federal de São Carlos, 2006-03-09) Corbi, Juliano José; Strixino, Susana Trivinho; https://lattes.cnpq.br/1804083229761186
Brazilian colonization occurred without a specific planning and, as a consequence, natural resources, particularly forests, were greatly affected specially by economic interests. In the Brazilian history, the native land cover vegetation was removed, and substituted by agriculture, mainly of sugar cane and also pastures. In the State of São Paulo, the sugar cane culture has also being enlarged, with the annual production of the about 200x106 tons covering an area of 2.5x106 ha. The use of herbicides and fertilizers containing different concentrations of the metals Pb, Ni, Cr, Cd and Zn, during different periods of cultivation of sugar cane, in addition to the deforestation of riparian vegetation, have caused impacts on the hydric resources of the adjacent areas. In the present work, the influence of the agricultural activity, in particular, sugar cane culture, on stream macroinvertebrate communities was studied. Macroinvertebrates, sediments and water were surveyed in three periods: March/April, 2002; June/July/August, 2002; October/November, 2002. Thirty three samples were collected: 15 in streams with sugar cane culture, 12 in streams with riparian vegetation and 6 in pasture areas. The concentration of the dissolved oxygen was low in streams without riparian vegetation (sugar cane and pasture) when compared to preserved areas. The concentration of the metals Cu, Fe, Cd, Zn, Mn, Cr e Ni of the sediment were high in streams with sugar cane cultivation, with significant differences to Cu and Zn, when compared to forested streams. The streams located in the adjacent areas with sugar cane cultivation also present high concentration and frequency of occurrence of the 15 organochlorine compounds analyzed. In this study, 3365 organisms were collected, in which 54 Chironomidae taxa and 42 of other aquatic macroinvertebrates. The streams located in areas of sugar cane culture and pasture (opened areas) presented low taxa and a great participation of Chironomidae (78% of the total). In contrast, the streams located in areas with riparian vegetation presented a rich aquatic fauna with less participation of Chironomidae (60% of the total). The community index, in addition to other measurements, applied to the stream macroinvertebrates community of the 11 streams pointed out to major values of richness, diversity and biotic index to the streams located on forested areas, when compared to the streams located on areas with sugar cane cultivation and pasture. Overall our results indicated that deforestation of the riparian vegetation was the principal aspect that influenced the stream macroinvertebrate communities. The loss of the riparian vegetation in the streams located adjacent of the agriculture areas establish an environmental impact that results in a poor taxa richness and shows clearly the necessity of a suitable management of the hydric resources of the southeast region of Brazil.
Existência global de soluções para uma classe de leis de conservação e algumas considerações sobre um sistema de leis de conservação
(Universidade Federal de São Carlos, 2006-03-09) Ferreira, Ricardo Edem; Kondo, Cezar Issao; https://lattes.cnpq.br/0900348462714778; https://lattes.cnpq.br/1696477429814262
In this work, we will construct global solutions for a conservation law, due to C. M. Dafermos. Also we will discuss some properties for a class of systems of conservation laws, due to B. Rubino.