The structure of the outer intermittent region of turbulent boundary layers with injection and suction through a slit.

Abstract

The structure of the outer intermittent region of non-equilibrium turbulent boundary layers disturbed by injection and suction through a slit is investigated experimentally. conditional sampling and averaging are used to generate mean and fluctuating components for the turbulent and non-turbulent zones of fluid. Further, space-time correlation is measured. The main results are summarized as follows: The center of intermittency moves outward from the wall, and the width of the intermittent zone decreases by the effect of injection. In the case of suction, the reverse characteristics, compared with injection, are observed. There exists a circulatory flow inside the turbulent bulge. This result is consistent with that of an equilibrium turbulent boundary layer. On the basis of the experimental results, a conceptual explanation for the development of the boundary layer and wall shear stress is discussed.