Spectral characteristics of turbulent boundary layers – comparison of Particle Image Velocimetry and Thermal Anemometry

Abstract

Flow in turbulent boundary layers over various rough surfaces was measured by the time-resolved particle image velocimetry and the thermal anemometry. The experimental methods showed very good agreement in both mean and spectral characteristics taking into account each method limitations. The spectral characteristics supported the attached eddy hypothesis. The most energetic structures were growing with the wall-normal distance and they achieved sizes equal to 3 to 8 boundary layer depths.