A Hybridizable Discontinuous Galerkin Method for the Miscible Displacement Problem under Minimal Regularity

Abstract. A numerical method based on the hybridizable discontinuous Galerkin method in space and backward Euler in time is formulated and analyzed for solving the miscible displacement problem. Under low regularity assumptions, convergence is established by proving that, up to a subsequence, the discrete pressure, velocity, and concentration converge to a weak solution as the mesh size and time step tend to zero. The analysis is based on several key features: an [Formula: see text] reconstruction of the velocity, the skew-symmetrization of the concentration equation, the introduction of an auxiliary variable, and the definition of a new numerical flux. Numerical examples demonstrate optimal rates of convergence for smooth solutions, and convergence for problems of low regularity.