On the scaling of turbulent separating boundary layers

This study focuses on the mean velocity distribution of turbulent boundary layers near, at, and after separation. The proper mean velocity scaling of the outer region in strong adverse pressure gradients and separated turbulent boundary layers is still under debate and over the years various different velocity scales have been proposed. Here the scaling proposed by Zagarola and Smits [J. Fluid Mech. 373, 33 (1998)] is applied to data from three different separated flows. In all cases the mean velocity defect profiles are self-similar in the region between separation and the position of maximum mean reverse flow. Downstream of the reverse flow maximum, the profiles change, but they are still self-similar within that region. It was also found that the mean velocity defect profiles of all three pressure gradients show similarity in the region between separation and the position of maximum mean reverse flow. (C) 2008 American Institute of Physics.