Convection velocity in turbulent boundary layers under adverse pressure gradient

The convection velocity (UC) of turbulent structures has been studied in adverse-pressure-gradient (APG) boundary layers (TBLs) for a wide range Reynolds numbers Reτ≈1400−4000. study is based on estimation the using decomposed streamwise skewness factor introduced (Dróżdż A., Elsner W., Int. J. Heat and Fluid Flow. 63 (2017) 67-74) verified by means two-point correlation method. It was shown that overlapping region APG flows, profiles (when scaled viscous units) reassemble universal logarithmic law characteristic ZPG flows up to Clauser-Rotta pressure gradient parameter β≲19 considered number, what inner TBL friction not proportional U (as ZPG) but UC instead. physical mechanism explains impact increased mean flow proposed. difference between increases as function APG, which causes stronger sweeping enhances momentum transfer wall compensates weaker shear profile created low vorticity near wall. This effect result an enhancement amplitude modulation small scales large-scale motion. process becomes more pronounced eddy density grows, so with increasing Re. proposed model addresses number literature observations found adverse have far left without well-founded explanation.