XVI CONGRESSO BRASILEIRO DE ENGENHARIA MECÂNICA 16th BRAZILIAN CONGRESS OF MECHANICAL ENGINEERING NUMERICAL SIMULATION OF UNSATURATED FLOW IN POROUS MEDIA USING A MASS-CONSERVATIVE MODEL

Water flow into unsaturated porous media is governed by the Richards’ partial differential equation expressing the mass conservation law and the Darcy ́s law. This equation may be written in three standard forms: the “h-based” form, the “θ-based” form, and the “mixed” form. Numerical aproximations based on different forms of this one-dimensional nonlinear equation can lead to significantly different results for unsaturated flow problems. In the h-based form generate poor results characterized by large mass balance errors and erroneous estimates of infiltration depth; whereas on the mixed form the mass is perfectly conserved, improving the accuracy of the results without requiring any additional computational effort. However, it is shown to be insufficient to guarantee good numerical solutions. In the present paper, the Richards’ equation is modeled in mixed form discretized by finite differences techniques using a backward Euler time-marching coupled with modified Picard method, and arithmetical mean in estimating of the hydraulic conductivity (K) between neighbors points of the mesh. Starting from this model, simulations were made to Dirichlet and Neumann boundary conditions, soil initially very dry and types of soil with different permeability. Besides, were tested interblocks weighting for estimating of K using experimental data and comparing them with quasi-analytical solution.