Vortex shedding and galloping of open semi-circular and parabolic cylinders in cross-flow

An experimental wind-tunnel study was undertaken to investigate the flow-induced vibration behaviour of open semi-circular and parabolic cylinders in cross-flow. The motivation for the research was to investigate the cause of the fatigue failures of a number of parabolic section rotary mixing blades in a large mixing vessel. Results are presented for force coefficients as a function of angle of incidence of the flow, Strouhal number and amplitude response. It is shown that the parabolic cylinder is subject to large amplitude vortex shedding resonance and, when the elastic axis is sufficiently downstream of the section's centre of gravity, galloping instability.