Effect of Reynolds number on turbulent boundary layer approaching separation

Abstract

The effect of Reynolds number on turbulent boundary layer under adverse pressure gradient has been barely investigated in the available literature. So far, experimental or numerical research on that issue were performed either for low Re or for low range of Re to capture its clear effect on flow statistics. Hence, the purpose of the present paper is to examine whether the effect of Reynolds number can be observed when much higher Re values and its much wider range, than previously investigated, are considered. Herein, the momentum loss thickness based Reynolds number Reθ was changed from 4900 to 14600. Such a wide range of Reθ appeared to be sufficient to capture an evident footprint of Reθ on the flow. It was found that the separation point is shifted downstream with increasing Reynolds number due to increased convection velocity close to the wall. More detailed studies of the skewness factor and premultiplied energy spectra revealed that this phenomenon can be attributed to enhanced, with increasing Re, large- and small-scale interactions commonly known as the amplitude modulation.