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This study is an experimental investigation of the fine structure of uniformly sheared turbulence within the framework of Kolmogorov’s local isotropy theory. The fine structure was invoked from statistics of derivatives and differences of the streamwise velocity, in both the streamwise and transverse directions, for turbulence Reynolds numbers Re[sub λ] between 140 and 660. The streamwise derivative had a pdf with highly asymmetrical, stretched tails, which became more pronounced as Re[sub λ] increased. Its skewness grew slowly with Re[sub λ], while its flatness increased at a higher rate, in conformity with previous studies. The transverse derivative had a pdf with a tail asymmetry that decreased as Re[sub λ] increased. Its skewness was positive and decreased from about 0.70 at Re[sub λ]=140 to about 0.34 at Re[sub λ]=660, while its flatness had values near 8.0 and increased only slightly with Re[sub λ]. The pdf and flatnesses of velocity differences suggested that intermittency in the inertial spectral range increased with a decreasing separation distance and increasing Re[sub λ]. Structure functions up to fourth order were compatible with Kolmogorov’s hypotheses, while the sixth-order structure functions required some correction. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The present study is concerned with scalar mixing in uniformly sheared turbulent flow, in which Reynolds stresses and integral length scales grow nearly exponentially. For this purpose, the high-velocity half of a uniformly sheared, turbulent air stream was heated electrically to a nearly uniform temperature, slightly above that in the other half, thus generating a thermal mixing layer between the heated and unheated streams. Measurements show that the mean temperature field reached a quasiasymptotic state, in which, to a first approximation, it maintained an error-function-like profile with a width that grew almost linearly within the range of measurements. The effects of shear were, however, manifested by an asymmetry of the mean temperature profile, indicating deeper penetration of the layer into the lower velocity side. Measurements of the evolution of rms temperature fluctuations, heat fluxes, third-order covariances, and length scales are also reported. Simple theoretical predictions of the evolution of the thermal mixing layer width and of temperature fluctuation statistics are also presented and shown to agree well with the measurements. [ABSTRACT FROM AUTHOR]