Simulação numérica do transporte de contaminantes em escoamentos bifásicos água-ar em meios porosos heterogêneos

• Autor(a) principal: Aquino, José Antônio Oliveira
• Data de Publicação: 2008
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/13708
• topic: Two-phase Flows; Central schemes for conservation laws; Lagrangian methods; Foward Integral-Tube Tracking Method (FIT); Escoamentos bifásicos; Esquemas centrais para leis de conservação; Lagrange, Funções de; Foward Integral-Tube Tracking Method (FIT); Equações diferenciais parciais não-lineares; Método dos elementos finitos; Escoamento em meios porosos; CNPQ::CIENCIAS EXATAS E DA TERRA::MATEMATICA::MATEMATICA APLICADA

In this paper is presented a new numerical simulator for the water-air two-phase flow and contaminant transport in unsaturated zone. It was used a decomposition of operators and implemented numerical methods suitable to the solution of each of the problems arising in this decomposition. The mathematical model consists of a system of nonlinear partial differential equations in the unknowns pressure, saturation and concentration with which one can determine the position of the contaminant as a function of time. A three-tier operators decomposition makes possible to use different time steps for different levels of decomposition. In the first two levels are solved the problems of velocity, transport and diffusion, to the problem of water infiltration underground. The third level is solved the problem of the transport of the contaminant from the calculated velocities and saturations on the solution to the problem of infiltration. The hybrid mixed finite element method is employed in numerical resolution of the problem of velocity-pressure and diffusive transport to the problem of infiltration. In the solution of the problem of convective transport, water-air two-phase flow, is used a central scheme of finite differences, not oscillatory and conservative. For the solution to the problem of contaminant transport is proposed a new Lagrangian method locally conservative, who received the denomination of Forward Integral-Tube Tracking Method (FIT). This new method is used in the numerical resolution of the convective transport of contaminant. The formulation, implementation and test of FIT is the main original contribution of this work. On verification and validation of the new numerical simulator, the results are compared with those from other experiments, simulators and from problems solved analytically. In all cases were obtained good concordances between the results of the new simulator and from others. The simulator has proved to be efficient in solving two-dimensional problems in saturated and unsaturated heterogeneous porous media, featuring mass conservation, low diffusion numerical and computational efficiency.