Interaction of flows behind two circular cylinders of different diameters in side-by-side arrangement

Abstract

Experiments were performed to study the fluid dynamics of flow past two cylinders of diameter ratio 1:2 in a side-by-side arrangement with a gap spacing of T/ D = 1.5. Based on hot-wire measurements and flow visualization results, the most frequent mode of large-scale flow structures in the wake consists of two vortex streets developed from the two cylinders. Behind the big cylinder the “first” (outer) and “second” (inner) streets are isolated. The former has a higher convection velocity, which is the same as that of the small cylinder's vortices, while the latter convects with a lower velocity. The big and small vortex streets interact in two stages, resulting in lateral transport of fluid across the entire widths of the two wake regions. A locked repetitive pattern of four big vortices with 10 small vortices is observed. A third spectral component behind the gap portion of the small cylinder's wake region is the consequence of the first-stage interaction. The less frequent mode does not suggest interaction of the big and small vortices.