Investigation of the Transitions to Turbulence Employing Simple Siphons

Reentrant tube siphons are amongst the simplest and experimentally most easily employed fluidics devices. Additionally, they have the potential to serve as a model system, supporting a common platform investigation of nonequilibrium processes, and potentially nonequilibrium phase transitions in the form of laminar to turbulent flow transitions. We report on our study of over 40 siphon tubes having diameters ranging from 0.16 to 1.27 cm, lengths of 3.0 to 30 m, and being operated at temperatures ranging from 10 to 30 C. The objectives of the study are two-fold, 1) to improve the understanding of the underlying physics and predictability of reentrant siphon tube performance, and 2) to measure and characterize the transition to turbulence in the 200 to 20,000 Reynolds number regime. The focus of the talk will be on our findings regarding turbulent structures and the observation of two modes of turbulence, first reported by Moss and others [1, 2]. We will present evidence that laminar flow to mode 1 turbulence disturbances, generated at tube entrances, transition from mode 1 to mode 2 turbulence, when the mode 1 disturbance washdown velocity exceeds twice the average flow velocity.



1 E.A. Moss, The identification of two distinct laminar to turbulent transition modes in pipe flows accelerated from rest, Exp. Fluids 7 (1989) 271–274.

2 J. Kurokawa, A. Takagi, Accelerated and decelerated flows in a circular pipe (2nd report, transition of an accelerated flow) (in Japanese), Trans. Jpn. Soc. Mech. Eng. 54B–498 (1988) 302–307