| Rain droplets impact on substrates is a very usual phenomenon.In cold and humid environments,it's easily freeze when rain droplets impacting on cold power line substrates.Icing phenomenon of power lines will commonly block the evoluation of electric-power industry and human's social life and production.In this paper,the dynamic and phase-change characteristics after water droplets impacting on cold power lines were studied.The dynamic characteristics of a water droplet impacting on smooth cylindrical substrates and smooth twisted substrates were studied by the CLSVOF method,respectively.Moreover,the dynamic and phase-change characteristics of water droplets impacting on cold smooth circular substrates were studied by the enthalpy-porosity method coupled with the CLSVOF method.In this paper,all numerical models were verified by the visual experiments.Main research contents are as follows:(1)By studying the processes of water droplets impacting on smooth cylindrical substrates,we got the effects of the surface wettability,the impact velocity and droplet-substrate relative size on droplet impacting dynamic characteristic.In the present study,we investigated solid-liquid contact area and residual liquid on the substrate which are key parameters to affect icing phenomenon of cylindrical power lines.(2)By studying the processes of water droplets impacting on smooth twisted substrates,we got the effects of the surface wettability and the impact velocity on droplet impacting dynamic characteristic.In the present research,we investigated solid-liquid contact area and residual liquid on the substrate which are key parameters to affect icing phenomenon of twisted power lines.(3)By studying the processes of water droplets impacting on cold smooth circular substrates,we got the effects of the temperature,the surface wettability and the impact velocity on droplet impacting dynamic and phase-change characteristics.In the present research,we investigated the height variation and wetting ability of liquid film in the impacting processes.Our investigations and concludes will provide references for the research of the phenomena of icing adhesion and accumulation after rain droplets impacting on power lines in cold and humid environments.It was found that the hydrophobic power lines can effectively reduce residual water adhesion and accumulation after water droplets impacting,and this can effectively reduce and delay icing phenomenon of power lines.The structure of power line substrates has great effects on the impacting dynamics of droplets on substrates.On cylindrical power lines,the impacting dynamics are regular,and include spreading,retracting,etc.The surface wettability has great effects on impacting dynamics on twisted power lines.The hydrophilic twisted power line is benefit for flowing of liquid along the concave grooved structure,which will enhance the attaching ability of impacting droplets.However,the hydrophobic twisted power line will enhance breaking ability of impacting droplets.Morever,it is found that the phase-change characteristic has great effects on dynamics after droplets impacting on cold power lines. |
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