Research on motion of wind-driven rain and rain load acting on transmission tower

This study derives the formula of rain load based on the motion state of droplets and the law of conservation of momentum to study the rain load acting on a transmission tower. By simulating the motion of a single raindrop, the phenomenon of that the horizontal velocity of raindrop is larger than the corresponding wind speed is certified and explained, and the fitting formula of the velocity ratio is obtained from simulation results. The specific catch ratio under uniform flow is derived and then extended to the atmospheric boundary layer wind field. The vertical raindrop spectrum is calculated with the specific catch ratios obtained from two different concepts. The formula for calculating rain load is derived based on the law of conservation of momentum, and a methodology for simulating a transmission tower’s response induced by wind and rain loads is presented. When the basic wind speed is 40 m/s, the maximum displacement percentages induced by rain loads relative to wind loads can only reach 1.78%. The results indicate that the influence of raindrop impinging force on a tower’s response during extreme weather conditions is not very significant and that more attention should be paid to the influence of rainfall on the aerodynamic property due to the existence of water film on the surface of tower and line.