Passive scalar cascades in rotating helical and non-helical flows

We study how helicity affects the spectrum of a passive scalar in rotating turbulent flows, using numerical simulations of turbulent flows with or without rotation and with or without injection of helicity. Scaling laws for energy and passive scalar spectra in the direction perpendicular to the rotation axis differ in rotating helical flows from those found in the non-helical case, with the spectrum of passive scalar variance in the former case being shallower than in the latter. A simple phenomenological model that links the effects of helicity on the energy spectrum with the passive scalar spectrum is presented. (paper)