Scaling laws and small-scale dynamics in rotating turbulence

P.D. MININNI

Colonia del Sacramento

Congreso; Fluidos 2010; 2010

Universidad de la República

Invariance properties of physical systems govern their behavior: energy conservation in turbulence drives a wide distribution of energy among modes, as observed in geophysical or astrophysical flows. In ideal hydrodynamics, the role of the invariance of helicity (correlation between velocity and its curl, measuring departures from mirror symmetry) remains unclear since it does not alter the energy spectrum. However, in the presence of rotation, significant differences emerge between helical and non-helical turbulent flows. In this talk we will briefly outline some results for these flows from phenomenological theory and numerical simulations, such as the resulting partition of energy and helicity among modes. Using massive numerical simulations, we will then show that small-scale structures and their intermittency properties differ according to whether helicity is present or not, in particular with respect to the emergence of laminar helical vortices with vertical updrafts in the helical case. Also, using simulations of rotating turbulence up to 15363 grid points, we will show that in helical rotating flows the direct cascade of energy to small scales is scale invariant and non-intermittent, whereas the direct cascade of helicity is highly intermittent. These results point to the discovery of a small parameter besides the Rossby number, which can be associated with the adimensionalized ratio of the energy to helicity flux to small scales.