| GAO Fang,ZHENG Jia-yi,LI Zhun,YU Yan-shun.Numerical Study on Droplet Self-transport on Composite Gradient Wedge-shaped Surface[J],51(11):405-411, 422 |
| Numerical Study on Droplet Self-transport on Composite Gradient Wedge-shaped Surface |
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| DOI：10.16490/j.cnki.issn.1001-3660.2022.11.038 |
| KeyWord:wettability gradient interfacial tension wedge-shape self-transport two-phase flow numerical simulation |
| Author | Institution |
| GAO Fang |
MIIT Key Laboratory of Thermal Control of Electronic Equipment, Nanjing University of Science and Technology, Nanjing , China |
| ZHENG Jia-yi |
MIIT Key Laboratory of Thermal Control of Electronic Equipment, Nanjing University of Science and Technology, Nanjing , China |
| LI Zhun |
MIIT Key Laboratory of Thermal Control of Electronic Equipment, Nanjing University of Science and Technology, Nanjing , China |
| YU Yan-shun |
MIIT Key Laboratory of Thermal Control of Electronic Equipment, Nanjing University of Science and Technology, Nanjing , China |
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| Abstract: |
| The control of droplets on heat transfer surfaces is crucial to the overall energy efficiency of the system, and self-transport of droplets can be controlled by surface wettability modification. Influenced by natural surfaces in nature, many scholars have introduced wetting gradients and wedge patterns to drive droplets to move on surfaces. Although the surface of the wetting gradient can realize the self-transportation of droplets, the bottleneck of the wettability range greatly limits the moving distance of the droplets. Droplet transport on the surface of the wedge pattern is restricted by the shape of the wedge, and larger wedge tip size is required for long-distance transport. This paper aimsto study the directional self-transport of droplets and further improve the self-transport rate of droplets, in addition to introducing wettability gradient and wedge-shape, and the two were combined on the surface. Based on the VOF (volume fluid model)model, a model suitable for the combination of wettability gradient and wedge-shape pattern is used to analyze the effects of wettability gradient and wedge angle on the droplet displacement by numerical simulation. The results show that the moving speed of the droplet can be effectively controlled by adjusting the wetting gradient and wedge angle. The unbalanced surface tension of the droplets increases with the wetting gradient, leading to higher moving velocities. The average velocity of the droplets on the surface with a wettability gradient of 15 (°)/mm was 42.3% and 130% faster than that on the surfaces of 10 (°)/mm and 5 (°)/mm. For larger wedge angle, although the speed of droplet was higher during the acceleration phase, it would stop earlier due to the loss of the driving force.The smaller wedge angle, the greater the displacement of the droplet. The droplet firstlystopped moving on the surface of 40° wedge angle, and the displacement on the surface of 20° wedge angle was 10.3% and 32.3% farther than that on the surface of 30° and 40° wedge angle, respectively. Due to the combination of the wettability gradient and wedge-shape on the composite gradient wedge-shaped surface, under the combined action of the unbalanced surface tension and the driving force formed by the wedge angle, the droplet moves faster and further on the composite gradient wedge surface. After combined wetting gradient and wedge pattern, droplets on 20° wedge angle surface at 15 (°)/mm and 10 (°)/mmcan move to the exit of the calculation model, and the average velocity of the droplet on the surface with 15 (°)/mm and 40° wedge angle reaches 292 mm/s, which is 37.7% higher than that of the single gradient surface and 175.5% higher than that of the single wedge pattern surface (20°).The composite gradient wedge-shaped surface that combined the wettability gradient and the wedge pattern can simultaneously reduce the bottleneck of the wettability range and the wedge shape restriction and improve the moving speed and distance of the droplets. The research results will help design efficient droplet transport functional surfaces and extend the fields of condensing devices, microfluidic devices, and drug detection. |
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