Anomalous scaling of passive scalars in rotating flows

PAOLA RODRIGUEZ IMAZIO; PABLO DANIEL MININNI

Geilo

Conferencia; The Geilo School 2011: Cooperative Phenomena in Flows; 2011

Institute for Energy and Tecnology

A passive scalar is a quantity diluted in a fluid in such a low concentration that it does not affect the flow evolution, but that it is advected and diffused by the flow. Examples are given by colorant dye used in experiments, and aerosols and pollutants in small concentrations in the atmosphere. In recent years, the study of passive scalars has been associated with substantial advances in our theoretical understanding of turbulent flows. In this work we present studies of the  scaling laws and the development of anisotropy for passive scalars and velocity in rotating turbulent flows. The passive scalar is more anisotropic than the velocity field, and its power spectrum follows a spectral law consistent with approx. k^-3/2. This scaling is explained with phenomenological arguments that consider the effect of rotation. Intermittency is characterized using scaling exponents and probability density functions of velocity and passive scalar increments. In the presence of rotation, intermittency in the velocity field decreases more noticeably than in the passive scalar. The scaling exponents show good agreement with Kraichnan´s prediction for passive scalar intermittency in two-dimensions, after correcting for the observed scaling of the second order exponent.