Sweeping decorrelation hypothesis in a turbulent round jet

Higher-order spectra and structure functions are used to investigate the random sweeping decorrelation hypothesis. Measurements in a turbulent round jet at moderate Taylor microscale Reynolds numbers (R-lambda = 230-545) indicate that higher-order (up to 4) velocity spectra and structure functions do not follow the Kolmogorov (1941a) scaling. The normal Reynolds stresses appear to influence the dynamics of the inertial range (IR). Spectra and structure functions of the transverse velocity fluctuation nu exhibit different behaviours from those of the longitudinal velocity fluctuation u. The extent of the -5/3 and 2/3 scaling ranges is greater for u than nu, and the compensated higher-order spectra of u collapse better than the corresponding nu spectra. Statistical independence between large and small scales implies a zero-correlation coefficient between velocity fluctuations and velocity increments. In the present moderate R, turbulent jet, the correlation coefficient is significant throughout the whole IR. The correlation coefficient between nu and the increment delta nu is larger than that between u and delta nu in the IR. Both correlation coefficients decrease as R-lambda increases. (C) 2001 Published by The Japan Society of Fluid Mechanics and Elsevier Science B.V. All rights reserved.