Amplification/suppression of flow-induced motions of an elastically mounted circular cylinder by attaching tripping wires

This study has experimentally studied the effect of tripping wires on the vibration of a circular cylinder subject to flows. We placed a pair of tripping wires onto the surface of a circular cylinder symmetrically about the stagnation point, and submerged the cylinder clamped or elastically mounted. The test for the clamped cylinder (hereinafter stationary cylinder test) covered a wide domain of angular position from 15° to 165° to find what angular positions enhance or weaken hydrodynamic forces acting on the cylinder. The test for the moving cylinder used four angular positions: 60°, 75°, 105° and 120° to examine how the tripping wires amplify or suppress the flow-induced vibration of the cylinder. The stationary cylinder test revealed that with the angular position ranging from 20° to 52.5° or greater than 97.5° the hydrodynamic forces diminish and with the angular position ranging from 52.5° to 97.5° the forces increase. Particularly, positioning the tripping wires at 75° maximally increases the lift and drag coefficients by 63% and 44%, respectively, in comparison with the coefficients produced without the tripping wires, and these coefficients are maximally reduced by 67% and 20%, respectively, by positioning them at 112.5°. The moving cylinder test has elucidated that the angular positions at 60° and 75° intensify the vibration of the cylinder, involving a monotonic increase in the amplitudes with an increase in reduced velocity and wide lock-in range. With the tripping wires attached at 105° and 120° the vibrations of the cylinder are considerably suppressed, particularly when the angular position is 120° the vibration completely disappears.