Propagation Velocity of Turbulent Slugs and Streaks in Transition Pipe Flow

Taking account of experimental observations on the transition process, an elementary theory is developed for estimation of propagation velocity of the rear end of turbulent slugs and streaks which constitute a major feature of the transition process in pipe flow. The theory gives a lower propagation velocity than observed experimentally within the lower range of transition Reynolds numbers while at higher Reynolds numbers the theory gives a value about 7% higher than obtained experimentally. These deviations are due to approximations in the analysis which cannot be avoided at the present level of information on the structure of turbulent shear.