Rainwater rivulets running on a stay cable subject to wind

Abstract

Stay cables are likely to vibrate under the combined effect of rain and wind in the so-called phenomenon rain–wind-induced vibrations (RWIVs). Rain takes part in the phenomenon in the shape of water rivulets that run along the cables. In previous articles, the authors investigated the conditions under which such rivulets can be formed. Using a lubrication model, it was shown for a particular wind–cable configuration that rivulets can only be exhibited above a critical wind speed for which gravity is overcome. The rivulets’ position was also predicted with the model. The results were validated by experiments. In this paper, the wind speed at which rivulets appear and their position are expressed for an arbitrary wind–cable orientation. A maximum wind speed for the rivulets’ existence is then estimated as the result of a balance between the drag force and the surface tension. A wind speed interval is consequently obtained for the rivulets’ appearance and maintenance on a cylinder. The boundaries of this interval are expressed in term of Weber numbers, comparing the surface tension and wind effect. These predictions are successfully compared with all the measurements that have been published in the literature.