Distribution and spanwise correlation of aerodynamic forces on a 5:1 rectangular cylinder in the vortex-induced vibration stage

Vortex-induced vibration (VIV) is a type of fluid–solid coupling vibration with a complex flow-field structure. Herein, the wall pressures around a 5:1 rectangular cylinder in the stationary and vibration states are studied via wind tunnel tests. By conducting the spectrum analysis, a novel method is proposed to divide the flow-field of the side surface into recirculation, main vortex, and reattachment regions. The method proposed can be used as a reference for partitioning the flow-field. Based on the partition results, the effects of the maximum amplitudes and development VIV stages on the spanwise correlations of the aerodynamic forces in different subregions are investigated. The results show that the correlation coefficients of the aerodynamic forces in all three subregions increase with the value of maximum amplitude, while the correlation coefficients in the stationary state are all the smallest. Additionally, the spanwise correlations are most affected by the maximum amplitude in the recirculation region and least affected in the main vortex region. Moreover, the maximum spanwise correlation coefficients in the three subregions do not appear at the maximum amplitude, but in the VIV rising stage, owing to the interaction between the self-excited force and vortex shedding force.