Higher-Order Correlations in a Turbulent Field

Abstract

Higher-order time-correlations and the associated skewnesses and flatnesses were measured in a turbulent field downstream of a grid using high-speed computing techniques. The results were obtained using samples of 160 020 digitized data recorded at time intervals of 1/12 800 sec during time periods of approximately 12.5 sec. Comparison is made between the measured correlations and the higher-order correlation curves corresponding to a Gaussian probability density distribution of turbulent velocities. The departures from Gaussianity are shown, and non-Gaussian probability distributions are proposed which correspond considerably better to experimental reality. Several relations between correlation coefficients of different orders are obtained for the non-Gaussian probability distributions and confirmed by comparison with the measured correlations, skewnesses, and flatnesses.