A New Analytical Formulation of Retention Effects on Particle Diffusion Processes.
Prof. Luiz Bevilacqua - Programa de Engenharia Civil - COPPE/UFRJ
Data: 11 / 06 / 2010 Hora: 14:00 h
Local: UFRJ, Centro de Tecnologia, Bloco G, sala 205.
A new analytical formulation to simulate diffusion with retention in a reactive medium under stable thermodynamic conditions is discussed. The analysis of diffusion with retention in a continuum medium is developed after the solution of an equivalent problem using a discrete approach. The ptoptosed law may be interpreted as the reduction of all diffusion processes with retention to a unifying phenomenon that can adequately simulate the retention effect namely a circulatory motion. It is important to remark that the theory deals with temporary retention, permanent retention is a sink which is different problem. It is remarkable that the governing equation requires a fourth order differential term as suggested by the discrete approach. The relative fraction of diffusion particles is introduced as a control parameter in the diffusion-retention law as suggested by the discrete approach. This control parameter is essential to avoid retention isolated from the diffusion process.That is retention is only possible in the presence of diffusion. Two matrices referring to material properties are introduced and related to the real phenomenon through the circulation hypothesis. The governing equation may be highly non-linear even if the material properties are constant but the retention effect is a function of the concentration level, that is, is a function of the concentration.