Compatibility conditions for the Stokes system discretized in 2-D Cartesian domains

Abstract The maximum number of independent numerical constraints that can be imposed on the velocity field is determined by identifying the compatibility conditions which arise between the discretized incompressibility constraint equations and the velocity boundary conditions. This number does not depend on the chosen numerical scheme and defines the maximum number of pressure modes that are numerically accessible. For the (Navier-)Stokes problem discretized in 2-D Cartesian domains, it is shown that, at most, N-8 pressure modes can be evaluated, N being the number of modes chosen for each velocity component. The eight out of access pressure modes are the so-called spurious pressure modes.