Abstract
An oscillation of exit streams, called flip-flop phenomenon, is seen in bundles of cylinders of various cross sectional geometry. There is no thorough understanding of the flow characteristics which lead to flip-flop oscillation phenomenon. In the present work, flow visualization by means of a laser Doppler velocimetry(LDV) was performed inside diamond-shaped cylinder bundles and the oscillating characteristics of the flip-flop flow exiting downstream were investigated by varying the row number and the gap in the cross section of flow passages of the bundles. It is disclosed that the turbulence characteristics in the wake flow behind cylinder vary with the row number. The critical Reynolds number for the evolution of the flip-flop flow is clarified in each geometry of diamond-shaped cylinders. The oscillating frequency in term of the Strouhal number for different cross sections of bundles is clearly correlated with the Reynolds number.
