Numerical study on surface-heterogeneity-induced anisotropic impact dynamics of droplet

2021 ◽  
Vol 44 ◽  
pp. 100495
Author(s):  
Li Jin ◽  
Yuxiang Wang
Author(s):  
Ledong Deng ◽  
Hong Wang ◽  
Zhu Xun ◽  
Rong Chen ◽  
Yudong Ding ◽  
...  

Abstract Ice adhesion and accretion on power lines is a severe problem that can pose a threat to the electric power transmission, and this icing phenomenon is significantly related to the impact dynamics of freezing rain droplets. In the current paper, this impacting process was studied by using computational fluid dynamics, and the model was verified by an experiment with a high-speed camera. The detailed droplet impacting processes on the surface of a very commonly used overhead power line (the ACSR-type cable) were analyzed. The effects of surface wettability (θ = 67–135 deg) and initial droplet impact velocity (We = 22–219) on the evolution of the liquid–solid contact area during the whole process and the volume of the residual liquid on the power line surface after impact were studied. Meanwhile, the influence of the surface structure of the ACSR power line on the droplet impact dynamics was analyzed. Results show that the capturing of impacting droplets can be enhanced by the grooved structures on a hydrophilic ACSR power line surface, while differently the expelling of impacting droplets can be enhanced by these grooved structures on a hydrophobic ACSR power line surface. By analyzing the possible influence of the surface structure of an ACSR power line on the phase transition of impacting droplets, these grooved structures could facilitate the formation of ice nucleation which can finally make the ice adhesion and accretion on an ACSR power line is more serious than that on a traditional smooth cylindrical power line.


1998 ◽  
Vol 77 (2) ◽  
pp. 473-484 ◽  
Author(s):  
M. Sampoli, P. Benassi, R. Dell'Anna,

2020 ◽  
pp. 57-65
Author(s):  
Eusébio Conceiçã ◽  
João Gomes ◽  
Maria Manuela Lúcio ◽  
Jorge Raposo ◽  
Domingos Xavier Viegas ◽  
...  

This paper refers to a numerical study of the hypo-thermal behaviour of a pine tree in a forest fire environment. The pine tree thermal response numerical model is based on energy balance integral equations for the tree elements and mass balance integral equation for the water in the tree. The simulation performed considers the heat conduction through the tree elements, heat exchanges by convection between the external tree surfaces and the environment, heat exchanges by radiation between the flame and the external tree surfaces and water heat loss by evaporation from the tree to the environment. The virtual three-dimensional tree model has a height of 7.5 m and is constituted by 8863 cylindrical elements representative of its trunks, branches and leaves. The fire front has 10 m long and a 2 m high. The study was conducted taking into account that the pine tree is located 5, 10 or 15 m from the fire front. For these three analyzed distances, the numerical results obtained regarding to the distribution of the view factors, mean radiant temperature and surface temperatures of the pine tree are presented. As main conclusion, it can be stated that the values of the view factor, MRT and surface temperatures of the pine tree decrease with increasing distance from the pine tree in front of fire.


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