A Two-Level Nonconforming Rotated Quadrilateral Finite Element Method for the Stationary Navier-Stokes Equations

In this paper, we propose a two-level nonconforming rotated finite element (TNRFE) method for solving the Navier-Stokes equations. A new nonconforming rotated finite element (NRFE) method was proposed by Douglas added by conforming bubbles to velocity and discontinuous piecewise constant to the pressure on quadrilateral elements possessing favorable stability properties. The TNRFE method involves solving a small Navier-Stokes problem on a coarse mesh with mesh size H and a large linearized Navier-Stokes problem on a fine mesh with mesh size h by the NRFE method. If we choose h=OH2, the TNRFE method gives the convergence rate of the same order as that of the NRFE method. Compared with the NRFE method, the TNRFE method can save a large amount of CPU time. In this paper, the stability of the approximate solutions and the error estimates are proved. Finally, the numerical experiments are given, and results indicate that the method is practicable and effective.