A study of the intermittent phases in the wall region of a turbulent flow

Most recent wall-turbulence studies have been performed at relatively low Reynolds numbers. The aim of the present investigation is to provide quantitative data on the evolution of the intermittent phases at higher Reynolds numbers. A conventional statistical analysis is presented; and the overall shape of the velocity probability density distributions is found to indicate the presence of intermittent phases, attenuated at higher Reynolds numbers. Two conditional sampling methods (Zaric's stochastic conditional sampling technique and a modification of Zaric's cyclic conditional sampling technique) are then used to detect the intermittent phases. The importance of each phase is delineated for the Reynolds numbers investigated (4.32 x 10 to the 4th, 10.39 x 10 to the 4th, and 17.7 x 10 to the 4th), and the relative importance of the two inrush and ejection phases is shown for each wall layer.