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A time stepping quasilinearization approach to the mixed (or coupled) form of one and two dimensional Richards' equations is developed. For numerical solution of the linear ordinary differential equation (ODE) for 1D case and elliptic for 2D case, obtained after this semidiscretization, a finite volume method is used for direct problems arising on each time level. Next, we propose a version of the decomposition method for the numerical solution of the inverse ODE and 2D elliptic boundary problems. Computational results for some soil types and its related parameters reported in the literature are presented. [ABSTRACT FROM AUTHOR]

The basic model motivating this work is that of contaminant transport in the Earth's subsurface, which contains layers in which analytical and semi-analytical solutions of the corresponding advection–dispersion equations could be derived. Then, using the interface relations between adjacent layers, one can streamline the study of the model to the solution to the initial boundary value problem for a coupled parabolic system on partitioned domains. For IBVPs, we set up weak formulations and prove the existence and uniqueness of solutions to appropriate Sobolev-like spaces. A priori estimates at different levels of input data smoothness were obtained. The nonnegativity preservation over time of the solution is discussed. We numerically demonstrate how to solve the reduced truncated problem instead of the original multispecies one with a large number of layers. [ABSTRACT FROM AUTHOR]

We consider fractional mathematical models of fluid-porous interfaces in channel geometry. This provokes us to deal with numerical identification of the external boundary conditions for 1D and 2D time fractional parabolic problems on disjoint domains. First, we discuss the time discretization, then we decouple the full inverse problem into two Dirichlet problems at each time level. On this base, we develop decomposition techniques to obtain exact formulas for the unknown boundary conditions at point measurements. A discrete version of the analytical approach is realized on time adaptive mesh for different fractional order of the equations in each of the disjoint domains. A variety of numerical examples are discussed. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel exponential difference scheme for solving non-linear problems arising in variably saturated flow with discontinuous absolute permeability. First, we derive the discretization for a linear convection-diffusion-reaction problem with discontinuous coefficients. Positivity preserving property, stability and convergence of the scheme are studied. Then, the method is implemented to the transport equation and Richards' equation. Various numerical experiments on graded and uniform meshes are presented and discussed. [ABSTRACT FROM AUTHOR]