Abstract
The interaction of vortex streets generated behind two circular cylinders in tandem arrangement is examined and discussed in terms of visualization experiments in a towing tank. The cylinder spacing parameter L/d is varied from 2.0 to 20.0 for the Reynolds numbers ranging between 40 and 300. The main interest of the study consists in the flow characteristics at the critical spacing where, according to many of the former experiments for the Reynolds numbers around 10 3-10 5, the curves of the Strouhal number and of the drag coefficient meet some marked discontinuity or jump. Another point of the paper is the complicated vortex interaction and the subsequent wake transformation observed at the level of the downstream cylinder for spacing ratios greater than the critical one. In order to support the analysis in some aspects, an image processing technique is applied to estimate quantitative distributions of stream function and vorticity within the vortex wake.
