Seyede Masoome Sadaghi - Road, Housing and Urban Development Research Center. Ministry of Road and Urban Development, Tehran, Iran,
Seyed Taghi Omid Naeeni - School of Civil Engineering, University of Tehran, Tehran, Iran
Hassan Yousefi - School of Civil Engineering, University of Tehran, Tehran, Iran

The vortex shedding from pipelines free span induces alternate hydrodynamic forces on the pipeline. The frequency of vortex shedding is of great importance inview of resonance phenomenon. Vortex shedding in oscillatory flows is more complicated because the near cylinder flow field has to rebuild itself twice percomplete cycle as the velocity reverses direction. In this paper, vortex shedding in oscillatory flow has been studied via multi-resolution method in which wavelettransform has been applied on the lift forces to reveal vortex shedding in simultaneous time-frequency domain.