title: Intermittency and coherent structures in the two-dimensional inverse energy cascade: comparing numerical and laboratory experiments.
abstract: We study the internal intermittency in the inverse energy cascade and in the condensation regime of two-dimensional turbulence, using physical and numerical experimental approaches. The analysis confirms that the velocity increments have nearly Gaussian distributions at all scales in the inverse cascade regime; it moreover shows that, in the condensation regime, the probability distribution functions of the velocity increments are non-Gaussian but do not significantly vary with the scale; it follows that one may consider that there is essentially no intermittency (in the usual sense), in the condensation regime. In both regimes, we emphasize that coherent structures (i.e., long-lived vortices) are clearly visible on the vorticity field, and we suggest the non-Gaussianity of the distributions in the condensation regime is due to the presence of a large-scale long-lived structures. The study is supplemented by the analysis of the distribution of energy transfers at various scales.
authors.affiliation: Laboratoire de Météorologie Dynamique, Ecole Normale Supérieure, 24 rue Lhomond, 75005 Paris, France.
authors.forename: T
authors.initials: T
authors.lastname: Dubos
authors.forename: A
authors.initials: A
authors.lastname: Babiano
authors.forename: J
authors.initials: J
authors.lastname: Paret
authors.forename: P
authors.initials: P
authors.lastname: Tabeling