https://scholars.lib.ntu.edu.tw/handle/123456789/598155
標題: | Splash of impacting nanodroplets on solid surfaces | 作者: | Wang Y.-B Wang Y.-F Wang X Zhang B.-X Yang Y.-R Lee D.-J Wang X.-D Chen M. DUU-JONG LEE |
關鍵字: | Atmospheric pressure;Drops;Hydrophilicity;Molecular dynamics;Rayleigh scattering;Reynolds number;Wetting;X ray microscopes;Harmonic vibration;Hydrophilic surfaces;Hydrophobic surfaces;Molecular dynamics simulations;Rayleigh-Taylor instabilities;Static contact angle;Surface wettability;Viscous dissipation rate;Hydrophobicity | 公開日期: | 2021 | 卷: | 6 | 期: | 9 | 來源出版物: | Physical Review Fluids | 摘要: | Using molecular dynamics (MD) simulations, this study investigates the splash of water nanodroplets on hydrophilic to hydrophobic surfaces with static contact angles ranging from 30 ° to 105 ° in the ranges of We=24.76-525 and Re = 18.43-65.51. Here, We is the Weber number, describing the ratio of inertial to capillary forces, and Re is the Reynolds number, defined as the ratio of inertial to viscous forces. Two splash patterns, internal breakup and prompt splash, are observed under normal conditions. The mechanisms behind these two patterns are found to be different from those of macroscale impacting droplets. The internal rupture of macroscale droplets is attributed to initial air holes on solid surfaces, whereas it arises from the vibration of a nanometer-thick spreading film for nanodroplets. The internal breakup of nanodroplets relies heavily on surface wettability because the attenuation of vibration is much more drastic on hydrophilic surfaces than hydrophobic surfaces owing to larger viscous dissipation rates. A damped harmonic vibration model is developed to characterize the vibration, which verifies the dependence of internal rupture on surface wettability. The prompt splash of macroscale droplets is initiated by air bubbles under the spreading lamella; however, the Rayleigh-Taylor instability of ejected rims caused by a rapidly decelerated spreading lamella gives rise to the prompt splash of nanodroplets. This mechanism is further verified by comparing the number of fingers predicted by the Rayleigh-Taylor instability theory with that obtained by MD simulations. Corona splash has been observed for macroscale droplets at standard atmospheric pressure conditions, but the present simulations show that an extremely high pressure of 1900 kPa is required to trigger it for nanodroplets. ?2021 American Physical Society. |
URI: | https://www.scopus.com/inward/record.uri?eid=2-s2.0-85114662555&doi=10.1103%2fPhysRevFluids.6.094201&partnerID=40&md5=c79721a6eaf300211d7b603aed940cb4 https://scholars.lib.ntu.edu.tw/handle/123456789/598155 |
ISSN: | 2469990X | DOI: | 10.1103/PhysRevFluids.6.094201 |
顯示於: | 化學工程學系 |
在 IR 系統中的文件,除了特別指名其著作權條款之外,均受到著作權保護,並且保留所有的權利。