  We introduce a mimetic dual-field discretization which conserves mass,
kinetic energy and helicity for three-dimensional incompressible Navier-Stokes
equations. The discretization makes use of a conservative dual-field mixed weak
formulation where two evolution equations of velocity are employed and dual
representations of the solution are sought for each variable. A temporal
discretization, which staggers the evolution equations and handles the
nonlinearity such that the resulting discrete algebraic systems are linear and
decoupled, is constructed. The spatial discretization is mimetic in the sense
that the finite dimensional function spaces form a discrete de Rham complex.
Conservation of mass, kinetic energy and helicity in the absence of dissipative
terms is proven at the discrete level. Proper dissipation rates of kinetic
energy and helicity in the viscous case is also proven. Numerical tests
supporting the method are provided.
