Numerical simulation of the airflow–rivulet interaction associated with the rain-wind induced vibration phenomenon

Rain-wind induced vibration is an aeroelastic phenomenon that occurs on the inclined cables of cable-stayed bridges. The vibrations are believed to be caused by a complicated non-linear interaction between rivulets of rain water that run down the cables and the wind loading on the cables due to the unsteady aerodynamic flow field. Recent research at the University of Strathclyde has been to develop a numerical method to simulate the influence of the external air flow on the rivulet dynamics and vice versa, the results of which can be used to assess the importance of the water rivulets on the instability. The numerical approach for the first time couples a Discrete Vortex Method solver to determine the external flow field and unsteady aerodynamic loading, and a pseudo-spectral solver based on lubrication theory to model the evolution and growth of the water rivulets on the cable surface under external loading. The results of the coupled model are used to assess the effects of various loading combinations, and importantly are consistent with previous full scale and experimental observations of rain-wind induced vibration, providing new information about the underlying physical mechanisms of the instability.