Time and frequency domain investigations of the velocity components in a turbulent boundary layer by means of LDV

Sudden spatial and temporal variations of the fluid-dynamic quantities can be observed in a turbulent boundary layer. Two points spatial velocity measurements are difficult to perform but can be obtained from the temporal ones by means of the Taylor hypothesis: the spatial field is supposed "frozen" to the temporal variation . Such a simplification has been tested through a comparison between the spatial and temporal correlations of the velocity components; the powerspectral distributions in the frequency domain have been also obtained. The LDA measurement technique allows to obtain also velocity data very close to solid walls in the viscous sublayer; the profilesof the first four statistical moments in the direction orthogonal to the wall have been measured.