A desertificação tornou-se tema relevante nos debates sobre a degradação das terras, feitos pela Organização Mundial das Nações Unidas, que é empenhada em, junto com os países afetados, combatê-la. As áreas criticamente atingidas pelo fenômeno no Brasil estão localizadas na região Nordeste. O estado do Rio Grande do Norte, por exemplo, apresenta uma área fortemente afetada, denominada de Núcleo de Desertificação do Seridó, compreendendo seis municípios. Este artigo tem como objetivo apresentar uma revisão de literatura sobre o processo de desertificação, com destaque para o panorama do fenômeno no estado do Rio Grande do Norte, na região do Seridó, especialmente no município de Parelhas. Sendo assim, o artigo poderá ser consultado como base para futuros estudos na área e em outros locais que apresentem características semelhantes.
The classic deep bed filtration model (CDBFM) has been widely used for predicting transport and retention of particulate suspensions in porous media. In the CDBFM, the filtration coefficient function is assumed to be dependent of the retained particle concentration, and the boundary conditions are fixed at the porous media inlet cross section. However, if particle retention is limited, no more retention occurs (filtration coefficient equals zero) in regions where maximum retention (jamming limit) is reached. In this article, a model for deep bed filtration considering limited retention is proposed and analytical solutions are obtained. In cases where jamming limit is reached, the well-known CDBFM and the proposed model significantly differ from each other. Contrary to the CDBFM solutions, the obtained solutions show that concentrations along porous media are highly influenced by maximum retention front, which propagates with velocity independent of filtration coefficient.
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