超声波激励下倾斜表面液滴逆重力迁移的润湿特性研究

Wetting Characteristics of Droplet Migration Against Gravity on Inclined Surfaces under Ultrasonic Excitation

摘要

为了研究35 kHz超声波激励下液滴在倾斜铝板表面逆重力迁移过程中的动态润湿行为，通过定量分析液滴体积、超声振动速度以及表面倾斜角对液滴直径铺展率及接触角滞后的影响，揭示了超声作用下液滴在倾斜表面逆重力迁移过程中的润湿行为演化规律，建立了液滴微观润湿特性与宏观动力学行为的协同作用关系。进一步基于受力竞争机制构建了包含声学韦伯数和邦德数的综合无量纲数，确立了液滴动力学响应的预测经验关系式。研究结果表明，超声激励可显著增强液滴润湿能力，并驱动液滴在30°、60°、90°倾斜表面实现逆重力迁移，最大位移约为5.04 mm。液滴直径铺展率在超声作用下呈现出增大-峰值-回缩-稳态的非线性演变，最大直径铺展率变化范围为1.16～1.51，且主要受超声振动速度正向调控。此外，超声振动可有效削弱重力诱导的润湿非对称性，推动接触角滞后由重力主导的负值状态向声场主导的正值状态转变，该转变临界值对应的综合无量纲数为18.79。该研究为基于声场的液滴输运与表面润湿调控提供了理论与实验依据。

Abstract

To investigate the dynamic wetting behavior of droplets migrating against gravity on an inclined aluminum surface under 35 kHz ultrasonic excitation,the effects of droplet volume,ultrasonic vibration velocity,and surface inclination angle on the droplet diameter spreading ratio and contact angle hysteresis are quantitatively analyzed.The evolution of the wetting behavior during droplet migration against gravity on the inclined surface is revealed,and the synergistic relationship between microscopic wetting characteristics and macroscopic dynamic behavior is established.Furthermore,based on the force competition mechanism,a combined dimensionless number involving the acoustic Weber number and Bond number is constructed,and an empirical relationship for predicting the droplet dynamic response is established.The results show that droplet wettability is significantly enhanced by ultrasonic excitation,and migration against gravity is achieved on surfaces inclined at 30°,60°,90°,with a maximum displacement of approximately 5.04 mm.Under ultrasonic excitation,the droplet diameter spreading ratio exhibits a nonlinear evolution of “increase-peak-retraction-steady state”,with the maximum diameter spreading ratio ranging from 1.16 to 1.51 and mainly increasing with ultrasonic vibration velocity.In addition,gravity-induced wetting asymmetry is effectively weakened by ultrasonic vibration,and contact angle hysteresis is shifted from a gravity-dominated negative state to an acoustic-field-dominated positive state.The combined dimensionless number corresponding to the critical transition is 18.79.A theoretical and experimental basis for acoustic-field-based droplet transport and surface wetting control is provided by this study.

关键词

超声波 / 倾斜表面 / 液滴 / 逆重力迁移 / 润湿特性

Key words

ultrasound / inclined surface / droplet / migration against gravity / wetting characteristics

参考文献

[1] 刘学,赖天伟,赵琪,等. 受限流道沿程参数变化对竖直圆管表面结霜特性影响的实验研究[J]. 西安交通大学学报, 2022,56(5):149-155.

[2] Liu Xue,Lai Tianwei,Zhao Qi,et al. Experimental study on effect of parameter variation along confined flow path on frosting characteristics of vertical circular tube surface[J]. Journal of Xi’an Jiaotong University, 2022,56(5):149-155.

[3] 谭海辉,陶唐飞,徐光华,等. 翅片管式蒸发器超声波除霜理论与技术研究[J]. 西安交通大学学报, 2015,49(9):105-113.

[4] Tan Haihui,Tao Tangfei,Xu Guanghua,et al. Ultrasonic defrosting theory and technology for finned—tube evaporator[J]. Journal of Xi’an Jiaotong University, 2015,49(9):105-113.

[5] 吴晓敏,褚福强,陈永根. 疏水表面结霜初期液滴生长的理论分析[J]. 化工学报, 2015,66(增刊1):60-64.

[6] Wu Xiaomin,Chu Fuqiang,Chen Yonggen. Theoretical analysis of droplets growth in early stage of frosting on hydrophobic surfaces[J]. CIESC Journal, 2015,66(S1):60-64.

[7] Ling Weihao,Wu Jingtao,Li Xuan,et al. Numerical prediction of frosting growth characteristics of micro—channel louvered fin heat exchanger[J]. Energy, 2023,283:128519.

[8] Vocale P,Morini G L,Spiga M. Influence of outdoor air conditions on the air source heat pumps performance[J]. Energy Procedia, 2014,45:653-662.

[9] Yeo L Y,Friend J R. Surface acoustic wave microfluidics[J]. Annual Review of Fluid Mechanics, 2014,46:379-406.

[10] Datta S,Sharma M,Das A K. Investigation of upward climbing motion of a droplet over an inclined surface using electrowetting[J]. Industrial & Engineering Chemistry Research, 2014,53(16):6685-6693.

[11] 高安然,李铁,刘翔,等. 基于温度梯度驱动的液滴传输行为研究[J]. 测试技术学报, 2010,24(5):377-380.

[12] Gao Anran,Li Tie,Liu Xiang,et al. Study on transportation behavior of droplet driven by thermal gradient[J]. Journal of Test and Measurement Technology, 2010,24(5):377-380.

[13] Seerha P P S,Kumar P,Das A K,et al. Proposition of stair climb of a drop using chemical wettability gradient[J]. Physics of Fluids, 2017,29(7):072103.

[14] Chamakos N T,Karapetsas G,Papathanasiou A G. How asymmetric surfaces induce directional droplet motion[J]. Colloids and Surfaces:A Physicochemical and Engineering Aspects, 2016,511:180-189.

[15] Yuan Zichao,Lu Chenguang,Liu Cong,et al. Ultrasonic tweezer for multifunctional droplet manipulation[J]. Science Advances, 2023,9(16):eadg2352.

[16] Luo Tao,Liu Sirui,Zhou Rui,et al. Contactless acoustic tweezer for droplet manipulation on superhydrophobic surfaces[J]. Lab on a Chip, 2023,23(18):3989-4001.

[17] Brunet P,Baudoin M,Matar O B,et al. Droplet displacements and oscillations induced by ultrasonic surface acoustic waves:a quantitative study[J]. Physical Review:E, 2010,81(3):036315.

[18] Chen Xi,Lal A. Surface liquid droplet motion on silicon ultrasonic horn actuators[C]//IEEE Ultrasonics Symposium, 2005.Piscataway,NJ,USA:IEEE,2005:1032-1035.

[19] Sesen M,Alan T,Neild A. Microfluidic on—demand droplet merging using surface acoustic waves[J]. Lab on a Chip, 2014,14(17):3325-3333.

[20] 吴馨,龚建英,靳龙,等. 超声波激励下铝板表面液滴群输运特性的研究[J]. 化工学报, 2023,74(增刊1):104-112.

[21] Wu Xin,Gong Jianying,Jin Long,et al. Study on the transportation characteristics of droplets on the aluminium surface under ultrasonic excitation[J]. CIESC Journal, 2023,74(S1):104-112.

[22] Galleguillos—Silva R,Vargas—Hernández Y,Gaete—Garretón L. Wettability of a surface subjected to high frequency mechanical vibrations[J]. Ultrasonics Sonochemistry, 2017,35(Part A):134-141.

[23] Guo Jiaojiao,Chen Xiaopeng,Shui Langquan. Surface wave mechanism for directional motion of droplet on an obliquely vibrated substrate[J]. Physics of Fluids, 2020,32(3):031701.

[24] Trapuzzano M,Tejada—Martínez A,Guldiken R,et al. Volume and Frequency—Independent spreading of droplets driven by ultrasonic surface vibration[J]. Fluids, 2020,5(1):18.

[25] Scortesse J,Manceau J F,Bastien F. Displacement of droplets on a vibrating structure[J]. Ultrasonics, 2002,40(1/2/3/4/5/6/7/8):349-353.

[26] Fukaya T,Kondoh J. Experimental consideration of droplet manipulation mechanism using surface acoustic wave[J]. Japanese Journal of Applied Physics, 2015,54(7S1):07HE06.

[27] De Jong E,Wang Ye,Den Toonder J M J,et al. Climbing droplets driven by mechanowetting on transverse waves[J]. Science Advances, 2019,5(6):eaaw0914.

[28] Sartori P,Quagliati D,Varagnolo S,et al. Drop motion induced by vertical vibrations[J]. New Journal of Physics, 2015,17(11):113017.

[29] Adachi K,Saiki K,Sato H,et al. Ultrasonic frost suppression[J]. Japanese Journal of Applied Physics, 2003,42(2R):682-685.

[30] Li Dong,Chen Zhenqian,Shi Mingheng. Effect of ultrasound on frost formation on a cold flat surface in atmospheric air flow[J]. Experimental Thermal and Fluid Science, 2010,34(8):1247-1252.

[31] Wang Dingyuan,Tao Tangfei,Xu Guanghua,et al. Experimental study on frosting suppression for a finned—tube evaporator using ultrasonic vibration[J]. Experimental Thermal and Fluid Science, 2012,36:1-11.

[32] Amer M,Wang Chichuan. Experimental investigation on defrosting of a cold flat plate via ultrasonic vibration under natural convection[J]. Applied Thermal Engineering, 2020,179:115729.

[33] Wu Xin,Gong Jianying,Gao Tieyu,et al. Experimental study on dynamic wetting behavior of liquid droplets on the aluminum surfaces excited by ultrasonic waves[J]. Applied Thermal Engineering, 2024,248(Part A):123209.

[34] Wu Xin,Gong Jianying,Jiang Zhen,et al. Droplet transport dynamics induced by ultrasonic vibration on horizontal metal surface[J]. Physics of Fluids, 2025,37(7):072116.

[35] Wu Xin,Gong Jianying,Wang Yutao,et al. Motion and rupture properties of droplets on inclined surfaces under ultrasonic excitation[J]. International Journal of Heat and Mass Transfer, 2026,256(Part 3):128108.

[36] 任政,张兴群,张蓓乐,等. —60 ℃水平圆管表面结霜特性的实验研究[J]. 西安交通大学学报, 2019,53(7):78-83.

[37] Ren Zheng,Zhang Xingqun,Zhang Beile,et al. Experimental study on the frosting behavior of horizontal circular tube surface at —60 ℃[J]. Journal of Xi’an Jiaotong University, 2019,53(7):78-83.

基金资助

国家自然科学基金资助项目(51776149)