VISUALIZATION OF THE SPANWISE CELLULAR STRUCTURE OF THE LAMINAR WAKE OF WALL-BOUNDED CIRCULAR-CYLINDERS

End effects give rise to cells of different frequencies appearing simultaneously across the span of a circular cylinder in the laminar Reynolds number range. Each cell is associated with a different angle between the vortex axis and the cylinder. Konig et al. [Phys. Fluids A 2, 1607 (1990)] suggested that the discontinuities in the Reynolds-Strouhal number relationship are due to the movement of the cell boundaries across the span with the Reynolds number. In this Letter, flow visualization of the parallel, intermediate, extreme and end-cell modes of vortex shedding supports these results.