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Experimental Investigation of Flow Around a Single Circular Cylinder Freely Vibrating in Two Degrees-of-Freedom


 Experimental investigations were performed for a single circular cantilevered cylinder located in a circulating water channel. The cylinder of mass ratio 1.78 and aspect ratio 17.8, vertically fixed at one end, was freely oscillating in the streamwise and lateral directions. Tests were performed at three reduced velocities of 1.29, 1.93, and 5.83, corresponding to Reynolds numbers 1.26 × 104, 1.88 × 104, and 5.65 × 104, respectively. At the inlet of the water channel, a Laser doppler velocimetry system measured mean velocities and turbulence intensities. Vortex shedding frequencies were compared with cylinder response frequencies in the streamwise and lateral directions. A particle image velocimetry technique analyzed the wake’s flow topology, and a triaxial accelerometer measured the cylinder response. Wake patterns of shed vortices caused by the flow around the cylinder were experimentally investigated. The main objective was to investigate wake patterns obtained for the stationary cylinder and for the cylinder oscillating with an elliptic trajectory and with a Lissajous trajectory. The PIV technique was used to capture vortex patterns on the mid plane along the cylinder’s length at three different time steps. The experiments provided reliable benchmark data suitable for numerical validation of vortex-induced vibration for circular cylinders oscillating in two degrees-of-freedom.