Flow-induced oscillations of a square cylinder due to interference effects

Measurements of the flow-induced oscillations of a spring-mounted square cylinder (test cylinder, side dimension B) due to the presence of a rigid square cylinder (interfering cylinder, side dimension b  ) are presented. Ratios of b/B=0.5b/B=0.5, 1.0, 1.5 and 2.0 have been used. Various relative positions of the test cylinder and the interfering cylinder, in tandem, side-by-side and staggered arrangements are considered (in all of the positions considered, the interfering cylinder was never upstream of the test cylinder). The results show that under certain combinations of the b/B ratio and the relative position, the test cylinder can experience oscillatory amplitudes almost three times those observed for the no-interfering case. Under certain other conditions, the vibrations are completely suppressed. The observed features are discussed with reference to earlier related studies. Flow visualisation results are obtained by using (a) stationary test cylinder and (b) oscillated test cylinder, to provide an explanation for the observed features.