A Visual Study of the Structures in Turbulent Pipe Flow

Abstract

The structure of a fully developed turbulent pipe flow is examined using the aluminum flake method at Reynolds numbers between 3000 and 15000. The aluminum flake method enables us to determine the current state of the flow. In the near-wall region there exists an array of small-scale streamwise vortex pairs. The average transverse spacing of the vortex pairs is about 64 ν⁄U_τ, where ν is the kinematic viscosity and U_τ the friction velocity. In the central region, however, the existence of coherent structures is not clear.