Abstract: A finite volume method is presented for the time dependent viscous incompressible flow around an in line oscillating circular cylinder at Reynolds number of 200、855 and 4 000.The N S equations in finite volume form are solved on a moving grid system, based on a time dependent coordinate transformation.To investigate the vortex shedding characteristics behind the circular cylinder and the effects of Reynolds number and other non dimensional parameters such as reduced amplitude and reduced frequency,several numerical schemes have been tested with different amplitudes and frequencies at each Reynolds number.Present numerical results indicate that several types of vortex shedding modes are mainly dependent on the reduced frequency and also the reduced amplitued,which is called synchronization or lock on.

Key words: circular cylinder, in line oscillating, vortex shedding, reduced frequency