Abstract
The results of a wind tunnel investigation on Strouhal frequencies of two identical, stationary, parallel circular cylinders arranged in staggered configurations, carried out in a uniform cross flow at a Reynolds number of 5.5×(10)^4,are presented in this paper. The new findings in this study are as follows. (i) When two cylinders are arranged with a stagger angle α=10°, there exists a superharmonic frequency on the inside surface of the downstream cylinder due to convective vortices from the upstream cylinder for spacing ratio of T/D>2.4 and bistable nature of flow for T/D<1.3. (ii) For α=25°, T/D=1.1∿1.8,a tristable nature of flow with regard to Strouhal number is detected by wavelet analysis, (iii) There exists a bistable nature of flow with regard to Strouhal numbers for α=45°, 60° and 75° in certain ranges of T/D.
