Incompressible pressure gradient turbulent boundary layers have been investigated experimentally at high Reynolds numbers within this work. A special focus has been on the impact of the characteristic intermittent feature of wall-bounded flows on statistics. As this requires accurate turbulent/non-turbulent interface (TNTI) detection, three suited interface detection approaches are compared to assess the sensitivity of the TNTI measurement of the method applied. The techniques considered are based on the turbulent kinetic energy, the homogeneity of the non-turbulent flow region, and the particle image density. The effect of bias errors on the TNTI measurement is particularly considered, but the implication of the results for the working range of the various techniques is also outlined. The analysis illustrates exemplary the sensitivity of the intermittency factor and the length of the TNTI with respect to the method applied. Based on these results, statistics conditioned to the interface are studied. Statistically analyzed are in particular velocity profiles and higher-order statistics as the turbulence intensity and the anisotropy of turbulent velocity fluctuations. Investigations revealed that fluctuating velocities obtained using the classical Reynolds decomposition are prone to error in the intermittent region due to the stochastic location of the interface in time. As a consequence, higher order statistics based on turbulent fluctuations were also biased. To address this issue, a conditioned Reynolds decomposition is analyzed and applied in this work, resulting in a revision of higher-order statistics as known from past studies. Through the combination of the developed methods, the clean turbulent and non-turbulent statistics reveal features, which aid understanding to turbulent wall-bounded flows. Besides the basic statistics, the large-scale coherence of streamwise velocity fluctuations is studied. In particular, the influence of velocity fluctuations, which only occur due to TNTI oscillations, is considered and the new results are analyzed with regard to the development of the turbulent superstructures.    «

Incompressible pressure gradient turbulent boundary layers have been investigated experimentally at high Reynolds numbers within this work. A special focus has been on the impact of the characteristic intermittent feature of wall-bounded flows on statistics. As this requires accurate turbulent/non-turbulent interface (TNTI) detection, three suited interface detection approaches are compared to assess the sensitivity of the TNTI measurement of the method applied. The techniques considered are bas...    »