Advection velocities of flow structures estimated from particle image velocimetry measurements in a pipe

Measurements with particle image velocimetry of a fully developed turbulent flow of water in a pipe with a Reynolds number of 5,370 are presented. The measurements are taken with a frame rate high enough to capture the same f low structure in two or three successive frames. It is thus possible to est imate the advection velocities of the flow structures. Ejection and sweep s tructures are identified and it is found that the average advection velocit ies for the structures were 80% and 87% of the centerline velocity for ejec tions and sweeps, respectively. An alternative analysis based on linear sto chastic estimation shows similar results.