Structures and Multipoint Correlators for Turbulent Advection: Predictions and Experiments

We present theoretical predictions and wind tunnel measurements of the 3-point correlator of fluctuating temperature in preheated turbulent flow. The dependence of this passive scalar correlator on the point configuration is calculated on the basis of a model Hopf operator describing its time evolution but can be understood in terms of the underlying frontlike structure of the temperature field. Model predictions reproduce the main features observed in experiment. The geometric insight into the structure of the fluctuating field provided by multipoint correlators suggests new approaches to the study of turbulence itself. (S0031-9007(98)07639-X) PACS numbers: 47.27.Ak, 02.50.Fz Turbulent advection and mixing is a technically im- portant problem in engineering (e.g., combustion) and in geophysical flows (e.g., dispersion of pollutants). The statistical properties of scalar fluctuations (e.g., tem- perature or the concentration of a pollutant) has many similarities with the statistics of the turbulent velocity field itself (1,2). Much work (3) has been devoted to under- standing the scaling properties of turbulent fields which deviate from the simple dimensional form predicted by the