Funnel-shaped vortical structures in wall turbulence

Publisher Website
Google Scholar
Abstract
The structure of the turbulent boundary layer in a horizontal open channel was investigated experimentally by means of laser Doppler anemometry (LDA) and by flow visualization synchronized with the LDA. These experiments indicate that the dominant structures in the wall region are large scale streamwise vortices which originate at the wall and grow and expand into the outer flow region. The shape of the vortices is that of an expanding spiral, wound around a funnel which is laid sideways in the direction of flow. Most of the observations of wall turbulence phenomena made over the years, such as quasistreamwise vortices, ejections, and sweeps seem to be part of these funnel-shaped vortices.