The production of turbulence near a smooth wall in a turbulent boundary layer

TLDR

The bubble data, though uncertain, uniquely provide time‑resolved velocity profiles and event sequences. The study emphasizes turbulence production near the wall and uses observations to discuss suitable mathematical models. The boundary layer over a flat plate in low‑speed water was examined with hydrogen‑bubble and hot‑wire measurements combined with dye visualization. In the near‑wall region (0 < y+ < 100), all turbulence production occurs during intermittent bursting, during which velocity profiles differ qualitatively from mean profiles.

Abstract

The structure of the flat plate incompressible smooth-surface boundary layer in a low-speed water flow is examined using hydrogen-bubble measurements and also hot-wire measurements with dye visualization. Particular emphasis is placed on the details of the process of turbulence production near the wall. In the zone 0 &lt; y + &lt; 100, the data show that essentially all turbulence production occurs during intermittent ‘bursting’ periods. ‘Bursts’ are described in some detail. The uncertainties in the bubble data are large, but they have the distinct advantage of providing velocity profiles as a function of time and the time sequences of events. These data show that the velocity profiles during bursting periods assume a shape which is qualitatively distinct from the well-known mean profiles. The observations are also used as the basis for a discussion of possible appropriate mathematical models for turbulence production.