Abstract. Efforts are made to explore the hysteresis characteristics of vortex shedding in a pipe flow, whose velocity varies periodically in time. Results obtained show that during acceleration of the flow, the vortex strength tends to be stronger, whereas during deceleration of the flow, the situation is reversed. As reconstructed from the velocity signals measured at a point in the flow field, the shed vortex arrays appear to possess uneven vortex strengths in response to periodically-varying incoming flows. Furthermore, in the hysteresis range, the streamwise spacings between the vortices appear to be unequal.

Keywords: Unsteady flow, Vortex shedding hysteresis, Vortex strength

Print publication: Issue 6 (December 2004)
Received 21 April 2003, revised 13 February 2004, accepted for publication 5 October 2004