Abstract
The three-dimensional velocity fluctuations of swirling incompressible flow in a smooth circular pipe are measured by the electrochemical technique and turbulent statistical quantities are studied.
It is proved that some turbulent statistical quantities (turbulent intensity and one-point double correlation) change by two different flow zones, that is, the forced vortex zone and the quasi-free vortex zone, which are distinguished by the time-averaged velocity distribution.
The diffusion of dye which is injected into the forced vortex zone is also discussed.
