Vibration of Beams and Trashracks in Parallel and Inclined Flows

The dynamic load and cross-flow response of trashrack bars and single beams subject to an incident flow was investigated for a wide range of cross-sectional shapes, bar spacings, and flow incidence angles. At zero flow incidence, rectangular profiles with a depth-to-thickness ratio less than six were found to be susceptible to two mechanisms of vortex-induced vibration: one due to Karman vortices, the other due to impinging leading-edge vortices. Longer rectangular profiles at zero flow incidence were stable. Rounding the edges, especially those facing the flow, resulted in an increased intensity of excitation due to Karman vortices. At small flow-incidence angles up to 15°, vortex excitation became weaker and turbulent buffeting set in. Reducing the bar spacing had a similar effect, attributable to the interference of adjacent bar wakes. Design recommendations are given to avoid serious flow-induced vibrations.