Pipe flow often traverses a regime where laminar and turbulent flow coexist. Prandtl and Tietjens explained this intermittency as a feedback between the fluctuations of the internal flow resistance and the constant pressure drop driving the flow. However, because the focus has moved towards studying intermittency without flow fluctuations near the universal critical Reynolds number, their explanation has largely disappeared. Here, we refine the mechanism, and put it to a quantitative test, to develop a model that agrees with experiments at higher Reynolds numbers, enabling us to demonstrate that Prandtl and Tietjens' mechanism is, in fact, intrinsic to flows where both the pressure gradient and perturbation are constant.

Close

PrevNext

View figure in article

• Flow instability
• Shear flows
• Transition to turbulence
• Turbulence