FLOW-INDUCED VIBRATION OF AN EULER–BERNOULLI BEAM

Flow-induced vibration of a fixed–fixed elastic cylinder with a large aspect ratio (≈58) is considered. The structural vibration is modelled by the Euler–Bernoulli beam theory, and the normal mode method is used to analyze the structural response. The flow field are resolved using a finite element method and the flow-induced forces are thereby calculated. Altogether two different cases are examined, one at resonance and another at off-resonance. Results thus obtained are compared with experimental measurements and a discrete-parameter model [a two-degree-of-freedom (2-d.o.f.) model] analysis. The comparison shows that, while the 2-d.o.f. model gives reasonable prediction of the mid-span vibration displacements for the resonant and off-resonant case, the present method yields the span-wise multi-mode response of the cylinder similar to that observed experimentally. Based on these results, a correction formula is derived to estimate the span-wise vibration from the 2-d.o.f. model result. Correlation results are also presented to show that fluid–structure interactions mainly affect the phase relation between the fluid forces and the corresponding vibration of the cylinder. Such influences have different effects along the cylinder span.