The effect of angle of attack on flow-induced vibration of low-side-ratio rectangular cylinders

This study investigates the effect of angle of attack on flow-induced vibrations (FIVs) of sharp-edged rectangular cylinders. In particular, the effect of the afterbody of a rectangular cross-section with low mass ratio and the side ratio ranging from 0.67 to 1.5 is analysed by changing the angle of attack with respect to the oncoming free-stream. As already shown for a different side ratio's rectangle, namely a square section (see Nemes et al., 2012), the angle of attack variation can make the flow-induced amplitude response switch between vortex-induced vibration (VIV) and galloping. Some considerations with respect to the interaction between the two phenomena typical of FIV, VIV and galloping, are also given for the side ratios of 1.5 and 0.67. The amplitude and frequency responses are carefully analysed, comparing the results with those of a square section of comparable mass ratio. The results showed a marked effect of the after-body, even for slight increments of the angle of attack. This can result in different amplitude response curves, as classified by the features of the response. In addition, the influence of interacting higher harmonics components on the amplitude response is also shown and discussed.