Spanwise correlation of vortex-induced forces on typical bluff bodies

Abstract

The spanwise correlation of vortex-induced forces (VIFs) on rectangular cylinders has been studied extensively. However, little knowledge exists regarding the differences and the evolution of the spanwise correlations of VIFs on blunt and streamlined bluff bodies. In this paper, wind tunnel tests were performed using the free vibration technique on three types of models in smooth flow. The models included a 4:1 rectangular (REC) cylinder, a trapezoidal (TRA) girder and a typical streamlined (STR) deck. Firstly, the vortex-induced pressure distribution was investigated at different attack angles for three models. The spanwise correlations of VIFs in different VIV stages were then studied in detail, along with the effects of VIV amplitude and attack angle. An interesting phenomenon was found in the REC and TRA models: the largest spanwise correlation appeared at the rising stage of VIV rather than at the peak oscillation amplitude. In addition, the spanwise correlations were preliminarily explained by the spectral analysis. The test results indicate that the spanwise correlations of the total VIFs may vary with the VIV stage, oscillation amplitude and changes in the cross-section configuration of bluff bodies.