  We introduce a finite volume scheme for the two-dimensional incompressible
Navier-Stokes equations. We use a triangular mesh. The unknowns for the
velocity and pressure are respectively piecewise constant and affine. We use a
projection method to deal with the incompressibility constraint. We show that
the differential operators in the Navier-Stokes equations and their discrete
counterparts share similar properties. In particular we state an inf-sup
(Babuska-Brezzi) condition. Using these properties we infer the stability of
the scheme.
