CONVERGENCE OF FOURIER METHODS FOR THE NAVIER-STOKES EQUATIONS

Optimal orders of convergence for the Fourier-Galerkin method for two- dimensional Navier-Stokes equations in various energy norms and in L(p )-norms of the velocity field are proved. Optimal orders of convergenc e for the Fourier-collocation method are also proved. Extensions of th ese results to three-dimensional Navier-Stokes equations in the origin al form and the rotational form are presented. Semigroup formulations and the variation of constants formula are the essential tools in the analysis.