Abstract
Free vibration tests of a sphere tethered in a vertical water tunnel were conducted at high Reynolds numbers. A 2m×2m square-section water tunnel and a sphere model of diameter 0.2m were used. Periodic vibrations of swirling mode were observed at sub-critical Reynolds numbers and the sphere drew circular or elliptical trajectories in the plane perpendicular to flow. Violent and less periodic vibrations were observed at the critical Reynolds number and the sphere contacted the side wall of the water tunnel; showing that the maximum displacement was well in excess of 4.5 times the sphere diameter.
