Transition from Turbulent to Laminar Pipe Flow

An experimental investigation of low-speed pipe flow was conducted for an initially turbulent flow of air. At subcritical Reynolds numbers, as the fluid traveled downstream its velocity profile approached the parabolic distribution corresponding to laminar flow; the rate of transition toward laminar flow being more rapid at lower Reynolds numbers. Concurrent hot-wire-anemometer measurements showed a corresponding dependence on Reynolds number of the rate of decay of the longitudinal velocity fluctuations. These velocity fluctuations were also found to decay more rapidly near the wall and center of the pipe than at intermediate radii. The energy spectrum of the fluctuations was measured along the pipe centerline, and, in terms of the macroscale, these spectra were similar.