Therefore, the cable vibration and upper rivulet oscillation interact and excite with each other. When they reach an equilibrium state, steady RWIV of cable occurs. The multi-amplitude RWIV under the same wind speed observed in Section 5.1 indicates that the equilibrium state might be non-unique. Different amplitude RWIVs could be caused by the small difference in initial conditions. The initial conditions of the upper rivulet and the cable vibration significantly affect the amplitude of RWIV. If the upper rivulet oscillation is uniform along the cable axis at the beginning even with small amplitude, the cable could tend to grow into large amplitude RWIV, and vice versa.