On wet and windy days, the inclined cables of cable-stayed bridges may experience a large amplitude oscillation known as Rain-Wind-Induced Vibration (RWIV). It has previously been shown by 'in-situ' and wind-tunnel studies that the formation of rain-water accumulations or 'rivulets' at approximately the separation points of the external aerodynamic flow field and the resulting effect that these rivulets have on this field may be one of the primary mechanisms for RWIV. A numerical method has been developed to undertake simulations of certain aspects of RWIV, in particular, rivulet formation and evolution. Specifically a two-dimensional model for the evolution of a thin film of water on the outer surface of a horizontal circular cylinder subject to the pressure and shear forces that result from the external flow field is presented. Numerical simulations of the resulting evolution equation using a bespoke pseudo-spectral solver capture the formation of two-dimensional rivulets, the geometry, location andgrowth rate of which are all in good agreement with previous studies. Examinations of how the distribution and magnitude of aerodynamic loading and the Reynolds number influence the rivulet temporal evolution are undertaken, theresults of which indicate that while all three affect the temporal evolution, the distribution of the loading has the greatest effect
