CLUSTERING OF INTENSE STRUCTURES IN ISOTROPIC TURBULENCE: NUMERICAL AND EXPERIMENTAL EVIDENCE

The spatial distribution of intense structures in isotropic turbulence is studied from numerical and experimental data. Box-counting of the intense vorticity and strain rate sets gives evidence of a strong clustering at intermediate scales, from which a possible fractal dimension can be defined. Algebraically distributed free intervals between intense velocity derivative from experimental time series confirms this self-similar clustering at larger Reynolds numbers, but without further specifying its dimensionality.