4233 The Development of Puffs and Slugs in Laminar-to-Turbulent Transition in Pipe Flow

Laminar-to-Turbulent transition of pipe flows occurs, for sufficiently high Reynolds numbers, in form of slugs. These form as intermittent disturbances in the entrance region of a pipe, grows in axial direction as they move downstream and join at some distance of the pipe inlet. In this way, the fully development of turbulent flow is formed in the far downstream region. This is shown in the paper and the merging of slugs from the entrance to the exit of pipe flows is quantified. A special flow test rig was developed and built for the described investigations and was employed for detailed investigations of laminar-to-turbulent transition studies. The paper also describes the triggered transition at relatively lower Reynolds numbers yielding the transition of puffs. They form by the introduced disturbances and developed afterwards into slugs with a higher front than back edge velocity. Thereafter the flow development occurs as found for slug flows.