Vortex Shedding Analysis in the Wake of a Rotating Cylinder*

A rotating cylinder can be used to generate an adverse pressure gradient (APG) for flat plate boundary layer studies. However, there must be certainty that wake fluctuations do not pollute the baseline boundary flow. Previous research has studied vortex shedding in an effort to understand and predict the flow past a rotating cylinder. However, experiments were performed largely at lower Reynolds’ numbers. A DPIV study of six velocity ratios (VR) ranging from 0 to 3.85 which were tested at Re = 4114 and 5500. Results were consistent with previous studies. As VR increased, vortices remained in closer proximity to the cylinder, and they were increasingly deflected at an angle off to one side. It was observed that VR > 2.0 is the critical value at which vortex shedding is suppressed. During boundary layer studies, a ratio of VR > 3.5 is used to induce an APG and cause flow separation conditions. In addition, results show that by this point the wake of the cylinder has been largely deflected outward and away from the flat plate. These results help validate the use of a rotating cylinder as a means to induce an APG without its wake interacting with the boundary layer during flat plate studies.