Energy cascade and intermittency in helically decomposed Navier-Stokes equations

We study the nature of the triadic interactions in Fourier space for three-dimensional Navier-Stokes equations based on the helicity content of the participating modes. Using the tool of helical Fourier decomposition we are able to access the effects of a group of triads on the energy cascade process and on the small-scale intermittency. We show that while triadic interactions involving modes with only one sign of helicity results to an inverse cascade of energy and to a complete depletion of the intermittency, absence of such triadic interactions has no visible effect on the energy cascade and on the inertial-range intermittency of the three-dimensional Navier-Stokes equations.