Characterization of high Reynolds number boundary layer by means of PIV
Since the study of Klebanoff the zero-pressure-gradient (ZPG) turbulent boundary layer (TBL) is one of the most investigated wall bounded flow. High accuracy ZPG TBL data are of great importance to highlight the influence of new parameters such as roughness, pressure gradient, etc.. However, the true statistics of a ZPG TBL is still often subject to controversies and this is particularly true at high Reynolds numbers. The first point of discrepancy is that it is often quite difficult to compare accurately the different experimental conditions under which a ZPG TBL develops. Comparisons of previous experimental data sets have shown significant discrepancies between different studies even if when the Reynolds number is the same. The quality of the free-stream flow is also of importance as external turbulence level or pressure gradient close to zero can have detrimentally affect the comparison. The classical way to compare results from different studies is to use a judicious scaling and to match the Reynolds numbers. In this case, the difference can come from either the accuracy of the measurement of the statistics, which is generally good, or from scaling parameters such as the friction velocity, which is used to normalize the profiles in the inner region. In the present study, the statistics are measured in the TBL wind tunnel of Lille for 3 nominal free-stream velocities at 3 streamwise stations in order to obtain 9 profiles over a large range of Reynolds numbers by using PIV. The main results will be discussed in the presentation.