FLOW-INDUCED OSCILLATIONS OF A CIRCULAR-CYLINDER DUE TO INTERFERENCE EFFECTS

Measurements of the flow-induced oscillations of a spring-mounted circ ular cylinder (test cylinder, diameter D) due to the presence of a rig id circular cylinder (interfering cylinder, diameter d) are presented. Ratios of d/D = 0.5, 1.0, 1.5 and 2.0 have been used. Various relativ e positions of the test cylinder and the interfering cylinder, in tand em, 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 combination s of the d/D ratio and the relative position, the test cylinder can ex perience 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 r eference to earlier related studies. Flow visualization results obtain ed by using a stationary test cylinder have provided a limited explana tion for the observed features.