Mixed finite element methods for the Oseen problem (Q780402)

In the paper the author reformulates the Oseen problem using tensor gradient of velocity as a new variable. This reduces the initial system of PDEs to a system of the first-order equations. In turn, these relations are rewritten in mixed form using scalar products in Sobolev spaces. It allows to use finite element method with Raviart-Thomas elements to solve the problem. In such a way all the desired functions will be approximated by piecewise continuous polynomials. The main result of the paper is power estimation of approximation errors.