Flutter of a semi-flexible cantilever in a cylinder's wake

We present an experimental study of the dynamics of flexible structures in a cylinder's wake using a vertical soap film tunnel. Experiments were conducted for two flexible cantilever beams of single rigidity modulus 6000 Pa mm⁴ with difference lengths resulting in Reynolds numbers 5000 < Re < 25000. Cantilevers at zero angle of attack were placed downstream of a cylinder with cylinder radii values ranging from 30-120% of the cantilever lengths. The study was conducted for three downstream gap distances from the cylinder's trailing edge to the cantilever's fixed leading edge. The cantilever motion and wake vortex structure are visualized and analyzed to estimate vibrational amplitudes, frequencies and aerodynamic loading. The beam vibration and vortex shedding results indicated possible flutter phenomena. Assuming small vibrational amplitudes, we consider the Euler-Bernoulli beam theory to estimate flutter derivatives. For the longer cantilever beam we observe evidence of second mode vibration as we increase Reynolds number.