Hysteresis at low Reynolds number: the onset of 2D vortex shedding

TL;DR

This paper investigates hysteresis phenomena in the transition from laminar flow to vortex shedding in a quasi-two dimensional soap film system, revealing that vortices can persist below the critical velocity for their formation.

Contribution

It demonstrates the existence of hysteresis in vortex shedding at low Reynolds numbers in a soap film system, highlighting a novel aspect of flow transition behavior.

Findings

Vortices can survive at velocities lower than those needed for their initial formation.

The transition between laminar flow and vortex shedding is hysteretic.

Hysteresis observed in a quasi-two dimensional soap film system.

Abstract

Hysteresis has been observed in a study of the transition between laminar flow and vortex shedding in a quasi-two dimensional system. The system is a vertical, rapidly flowing soap film which is penetrated by a rod oriented perpendicular to the film plane. Our experiments show that the transition from laminar flow to a periodic K\'arm\'an vortex street can be hysteretic, i.e. vortices can survive at velocities lower than the velocity needed to generate them.