LDA SPECTRAL MEASUREMENTS IN A TURBULENT BOUNDARY-LAYER

Fluid velocity measurements in a turbulent boundary layer are performed by means of laser-Doppler anemometry (LDA) in order to analyze, in the time and frequency domain, the trend of turbulent quantities very close to the wall; a large number of data are achieved at a high rate. Three velocity components are simultaneously measured using two independent LDA systems; correlation and spectral density functions together with integral and Taylor time scales at each distance from the wall are calculated. An evaluation of the amplitude of the anisotropic region in the frequency domain is also performed.