摘要：In several papers published since the early eighties, the author demonstrated that some mixed finite element methods to solve two-dimensional viscous incompressible flow equations in primitive variables with a conforming velocity, have non-conforming three-dimensional analogues. Parallelly he established that some classical non-conforming two-dimensional methods in other formulations admit non trivial equivalent extensions to the three-dimensional case. In this work, while recalling some of the above mentionned examples, the author exhibits a case where a fundamental property of a three-dimensional non-conforming method does not hold for its analogous two-dimensional version. This property is shown to play a crucial role in connection with the Navier-Stokes equations in terms of a vector potential with a vanishing gradient on the boundary of the flow domain.
