CONVERGENCE ANALYSIS OF THE MIMETIC FINITE DIFFERENCE METHOD FOR ELLIPTIC PROBLEMS WITH STAGGERED DISCRETIZATIONS OF DIFFUSION COEFFICIENTS

We study the convergence of the new family of mimetic finite difference schemes for linear diffusion problems recently proposed in [K. Lipnikov, G. Manzini, J. D. Moulton, and M. Shashkov, J. Comput Phys, 305 (2016), pp. 111-126]. In contrast to the conventional approach, the diffusion coefficient enters both the primary mimetic operator, i. e., the discrete divergence, and the inner product in the space of gradients. The diffusion coefficient is therefore evaluated on different mesh locations, i. e., inside mesh cells and on mesh faces. Such a staggered discretization may provide the flexibility necessary for future development of efficient numerical schemes for nonlinear problems, especially for problems with degenerate coefficients. These new mimetic schemes preserve symmetry and positive-definiteness of the continuum problem, which allow us to use efficient algebraic solvers such as the preconditioned conjugate gradient method. We show that these schemes are inf-sup stable and establish a priori error estimates for the approximation of the scalar and vector solution fields. Numerical examples confirm the convergence analysis and the effectiveness of the method in providing accurate approximations.