Comparative Analysis of End Conditions on Vortex Shedding from a Circular Cylinder in Sub-Critical Flow

In this experimental study, we examine the effect of several end conditions on a circular cylinder in subcritical cross flow. Measurements are performed in a water tunnel with removable top section. The end conditions considered in this study include the free-surface, direct wall mount, end plates of various geometries and fetch, as well as an upstream control device. A range of Reynolds numbers is considered from 3000 to 30000. The variation in the mean flow structure is examined in terms of the ensemble averaged streamwise velocity along the cylinder axis. This analysis demonstrates that the vortex confluence point is highly sensitive to end condition, and varies about the span. Further insight into the effect of end conditions is drawn from a time-resolved analysis of the vortex filament, which is captured from PIV data obtained along the axial and streamwise flow direction. Particular focus is given to the analysis of the axial variation in what is denoted as the vortex filament. Identification methods are used to show that this parameter exhibits sensitivity to both end conditions and Reynolds number.