Filtering of the pressure spurious modes in P_N-P_N spectral approximations of the Stokes system

In the framework of Jacobi polynomials based spectral methods, the P_N-P_N approximation of the Stokes system generally shows the drawback that the pressure kernel does not reduce to the constant field. However, this drawback goes together with the advantage that the velocity field may be perfectly solenoïdal, i.e. the divergence of the velocity is the null polynomial. In this paper we suggest a filtering algorithm to recover the pressure in an efficient way.