Critical spacing of stationary tandem circular cylinders at Re≈100

Abstract For steady flow past two stationary circular cylinders that are aligned in tandem with their axes perpendicular to the flow direction, the wake pattern, vortex shedding frequency, and forces on the cylinders typically show an abrupt change as a function of the dimensionless center-to-center cylinder spacing over a range of critical spacing values. For R e ≲ 190 , the flow is expected to be laminar and two dimensional, and hence well behaved, yet prior experimental and computational results do not agree regarding the value of the critical spacing, l c . Using flow visualization techniques in a flowing soap film system with R e = 99 ( ± 8 ) , we found the experimental critical spacing range to be 2 . 9 ≲ l c ≲ 4 . 1 , lower than prior experimental results and consistent with published computational results.