Abstract
In this study, the flow features of vortex shedding from a square cylinder forced-oscillating in the in-line direction were investigated by use of flow visualization technique at the Reynolds number Re=1004,with six kinds of amplitude ratio and the range of oscillation frequency ratio from 0.0 to 12.7. As a result of the experiments, six kinds of representative flow patterns were observed. In the case of the smallest amplitude ratio 2a/h=0.0353,there was not an influence of the cylinder oscillation to the mean vortex shedding frequency. It was found that when the oscillation amplitude ratio 2a/h becomes large, the frequency ratio which the lock-in occurs to becomes small and even if the cylinder oscillation frequency is smaller than the natural Karman vortex shedding frequency, The lock-in phenomenon arises. The flow pattern map in the lock-in region was shown.
