中文摘要：

<正>This paper considers the mixed covolume method for the second-order elliptic equations over quadrilaterals.Superconvergence results are established in this paper on quadrilateral grids satisfying the h~2-parallelogram condition when the lowest-order Raviart-Thomas space is employed in the mixed covolume method.The authors prove O(h~2) accuracy between the approximate velocity or pressure and a suitable projection of the real velocity or pressure in the L~2 norm.Numerical experiments illustrating the theoretical results are provided.

英文摘要：

This paper considers the mixed covolume method for the second-order elliptic equations over quadrilaterals. Superconvergence results are established in this paper on quadrilateral grids satisfying the h2-parallelogram condition when the lowest-order Raviart-Thomas space is employed in the mixed covolume method. The authors prove O（h2） accuracy between the approximate velocity or pressure and a suitable projection of the real velocity or pressure in the L2 norm. Numerical experiments illustrating the theoretical results are provided.