Release Time:2019-03-11  Hits:

Indexed by: Conference Paper

Date of Publication: 2016-01-01

Included Journals: SCIE、CPCI-S

Page Number: 429-434

Key Words: Oscillation; Lock-on; Synchronization; Flow structure

Abstract: This study presents the vortex formation in the wake of a cylinder undergoing streamwise oscillations in steady flow. It is found that the global wake structure possesses a spatial-temporal symmetry over N periods of cylinder oscillation when sub-harmonic synchronizations occur. The sub-harmonic synchronization modes are characterized by shedding of M pairs (1 <= M < N) of vortices in N periods of cylinder oscillation. The wake of M/N modes is comprised of vortex groups of M vortices arranged in a similar way to Karman vortex street. The lift force shows excellent periodicity when lock-on occurs, and presents multiple peaks in its spectrum. The primary flow mechanism responsible for the sub-harmonic lock-on is identified as the interaction of the small sized shear bands induced by the cylinder oscillation with the shear layers induced by the steady flow.