Statistical characteristics of Reynolds stresses in a turbulent boundary layer

Measurements are presented of autocorrelations and spectra of the Reynolds normal and shear stress fluctuations in a turbulent boundary layer. The measurements in the fully turbulent part of the layer are in good agreement with calculations which assume a Gaussian probability density of the individual velocity fluctuations and a joint Gaussian probability density for these fluctuations. The measured spectral densities scale reasonably well with freestream velocity and boundary-layer thickness over the whole frequency range, throughout the boundary layer.