Fluid behaviour of side-by-side circular cylinders in steady cross-flow

The flow held for two and three circular cylinders of equal diameter D arra nged in a side-by-side configuration in steady cross-flow was investigated using flow visualization, hot-film anemometry and particle image velocimetr y (PIV), for centre-to centre pitch ratios from T/D = 1.0 to 6.0, and Reyno lds numbers from Re = 500 to 3000. For two-cylinder arrangements, three bas ic how patterns were observed: single bluff-body vortex shedding at small T /D, biased how with synchronized vortex shedding at intermediate T/D, and s ymmetric flow with synchronized vortex shedding at larger T/D. For three-cy linder arrangements, either single bluff-body behaviour or an asymmetric bi ased how pattern could be observed at small T/D, whereas a symmetric-biased flow pattern was found at intermediate T/D. Instantaneous representations of the in-plane vorticity field obtained from the PIV technique revealed so me variation in these basic flow patterns at given T/D and Re. (C) 1999 Aca demic Press.