Some vortex-shedding characteristics of the staggered configuration of circular cylinders

A pair of circular cylinders of equal diameter, arranged in. the staggered configuration was tested in the subcritical Reynolds number regime at centre-to-centre pitch ratios of P/D = 2.0 and 2.5. For each pitch ratio, the incidence angle was varied in small steps in the range alpha = 0-90degrees. Vortex-shedding frequency measurements were made behind the upstream and downstream cylinders as the incidence angle, alpha was varied. At,small incidence angles, 2degrees<α<15degrees, the Strouhal number data were unreliable, since the peaks in the power spectra were either absent or broad banded. In this same range of incidence angle, the downstream cylinder experiences a maximum inward-directed lift force and a minimum drag force. The results indicate that the flow mechanisms responsible for the changes in the aerodynamic forces have an important influence on the vortex-shedding activity also. (C) 2003 Elsevier Science Ltd. All rights reserved.