The deterioration occurs due to a consistency error associated with the boundary layer - we show how a modification of the elements at the boundary can fix the problem. This scheme is based on the decoupled computation of the new velocity-field and pressure iterates by means of Chorin's projection method. Second, a thorough analysis of this scheme is given that leads to optimal error statements which apply to general flow situations. The representation used involves only single and double layer potentials and does not require the discretization of the hypersingular integral operator as in the symmetric formulation. The stability of the hybrid Galerkin discretization is based on a BBL- like stability condition for the trial spaces.
Numerical examples confirm the theoretical results.