Approach to isotropy in a smooth wall turbulent boundary layer

Abstract

The approach to local isotropy in a smooth wall turbulent boundary layer is examined using measurements of velocity spectra and moments, up to order 4, of velocity increments. The ratio of the measured spectrum of the wall normal velocity fluctuation v to that calculated using isotropy from the measured spectrum of the longitudinal velocity fluctuation u, depends mainly on the Kolmogorov-normalized local mean strain rate and the Taylor microscale Reynolds number. These parameters also affect in a systematic way the departure from isotropy of the u− v spectral correlation coefficient and of the v increment moments.