Excitation mechanism of rain-wind induced cable vibration in a wind tunnel

The rain-wind induced vibration (RWIV) of cables in bridge and wind engineering has been reported worldwide over the past decades. However, quantitative analyses of the RWIV mechanism using the real water rivulets are rare. The RWIV of a cable model is tested in an open-jet wind tunnel. The movement and the geometry of the upper rivulet and the vibration of the cable are obtained by videogrammetry. The coupling of the upper rivulet and cable vibration is shown to be the main excitation mechanism of RWIV. In particular, the oscillating upper rivulet induces the boundary layer to attach to the cable and generates aerodynamic forces, which produce a positive work and excite the cable to vibrate. In turn, the cable vibration harmonizes the upper rivulet along the cable. To verify the proposed mechanism, a numerical model is established using the aerodynamic coefficients measured in dry cable tests. The numerical results are in agreement with the experiments. The effect of the damping ratio on the RWIV amplitude is also experimentally and numerically investigated.