Transactions of the Korean Society of Mechanical Engineers B (대한기계학회논문집B)

The Korean Society of Mechanical Engineers (대한기계학회)
권호 표지
DOI QR코드

DOI QR Code

Study on the Pattern of Internal Flow inside a water droplet placed on Vibrating Hydrophobic Surface

진동하는 소수성 표면 위에 놓인 액적의 모드별 내부유동 패턴변화에 관한 연구

  • Kim, Hun (School of Mechanical Engineering, Pusan Nat'l Univ.) ;
  • Shin, Young Sub (School of Mechanical Engineering, Pusan Nat'l Univ.) ;
  • Lim, Hee Chang (School of Mechanical Engineering, Pusan Nat'l Univ.)
  • 김훈 (부산대학교 기계공학부) ;
  • 신영섭 (부산대학교 기계공학부) ;
  • 임희창 (부산대학교 기계공학부)
  • Received : 2013.11.13
  • Accepted : 2014.02.04
  • Published : 2014.04.01
Download PDF
⟨ Previous Next ⟩

Abstract

This study aimed to understand the internal flow characteristics of a liquid droplet subject to periodic forced vibration. In order to predict the resonance frequency of a droplet, a high-speed camera and macro lens were used to capture internal flow characteristics of a droplet placed on a vibrating hydrophobic surface. Results showed that the droplet assumed a variety of shapes depending on the resonance mode of free droplet, particularly in modes 2, 4, 6, and 8. In addition, the induced internal vortex flow inside the droplet was also observed in each mode. Typically, the induced flow moved upwards along the axis of symmetry and downwards along the surface of the droplet, that is, from the apex to the contact line in modes 2 and 4, after which it broke into a smaller vortex. On the other hand, the large-scale vortex always remained steady in modes 6 and 8. The speed of the flow in mode 4 was always greater than that in mode 2, but those in modes 6 and 8 were similar.

본 연구의 목표는 주기적으로 강제 진동하는 소수성 표면위에 놓인 액적의 내부유동 특성을 이해하는 것이다. 액적의 공진주파수를 예측하기 위해서 고속카메라와 매크로렌즈를 사용하여 진동하는 소수성 표면위의 액적의 내부유동 특성을 확인하였다. 그 결과 특정 모드에서의 액적은 다양한 형상을 갖고 있으며 또한, 각각의 액적 내부에서 와류가 관찰 되었다. 일반적으로 유동흐름이 대칭축을 따라 위로 이동하고 액적상단에서 표면을 따라 접촉선부근으로 이동하였다. 반면에 모드 6과 모드 8에서는 아주 큰 와류가 생성되었다. 또한 유동속도가 모드 2보다 모드 4에서 더 빠르고 반면에 모드 6와 모드 8은 거의 비슷하였다.

Keywords

References

  1. Kelvin, 1890, Mathematical and Physical Papers, Vol. 3, Clay, p. 384.
  2. Rayleigh, L., 1894, The Theory of Sound, Macmillan, New York.
  3. Strani, M. and Sabetta, F., 1984, "Free Vibrations of a Drop in Partial Contact with a Solid Support," J. Fluid. Mech, Vol. 141, pp. 233-247. https://doi.org/10.1017/S0022112084000811
  4. Daniel, S., Sircar, S., Gliem, J. and chaudhury, M. K., 2004, "Ratcheting Motion of Liquid Drops on Gradient Surfaces," Langmuir, Vol. 20, pp. 4085-4098. https://doi.org/10.1021/la036221a
  5. Daniel, S., Chaudhury, M. K. and De Gennes, P. G., 2005, "Vibration-actuated Drop Motion on Surfaces for Batch Microfluidic Processes," Langmuir, Vol. 21, pp. 4240-4248. https://doi.org/10.1021/la046886s
  6. Dong, L., Chaudhury, A. and Chaudhury, M. K., 2006, "Lateral Vibration of a Water Drop and its Motion on a Vibrating Surface," Eur. Phys. J. E, Vol. 21, pp. 231-242. https://doi.org/10.1140/epje/i2006-10063-7
  7. Noblin, X., Buguin, A. and Brochard-Wyart, F., 2009, "Vibration of Sessile Drops," Eur. Phys. J. Special Topics, Vol. 166, pp. 7-10. https://doi.org/10.1140/epjst/e2009-00869-y
  8. Brunet, P., Eggers, J. and Deegan, R. D., 2009, "Motion of a Drop Driven by Substrate Vibrations," Eur. Phys. J. Special Topics, Vol 166, pp. 11-14. https://doi.org/10.1140/epjst/e2009-00870-6
  9. Hong, F. J., Jiang, D. D. and Cheng, P., 2012, "Frequency-dependent Resonance and Asymmetric Droplet Oscillation Under ac Electrowetting on Coplanar Electrodes," J. Micromech. Microeng, Vol. 22, pp. 1-9.
  10. Oh, J. M., Ko, S. H. and Kang, K. H., 2008, "Shape Oscillation of a drop in ac Electrowetting," Langmuir, Vol. 24, pp. 8379-8386. https://doi.org/10.1021/la8007359
  11. McHale, G., Elliott, S. J., Newton, M. I., Herbertson, D. L. and Esmer, K., 2009, "Levitation-Free Vibrated Droplets: Resonant Oscillations of Liquid Marbles," Langmuir, Vol. 25, pp. 529-533. https://doi.org/10.1021/la803016f
  12. Depaoli, D. W., Feng, J. Q., Basaran, O. A. and Scott, T. C., 1995, "Hysteresis in Forced Oscillations of Pendant Drops," Phys. Fluids, Vol. 7, pp. 1181-1183. https://doi.org/10.1063/1.868576
  13. Wilkes, E. D. and Basaran, O. A., 1997, "Forced Oscillations of Pendant (Sessile) Drops," Phys. Fluids, Vol. 9, pp. 1512-1528. https://doi.org/10.1063/1.869276
  14. Kim, H. Y., 2004, "Drop Fall-off from the Vibrating Ceiling," Phys. Fluids, Vol. 14, pp. 474.
  15. Brunet, P., Eggers, J. and Deegan, R. D., 2007, "Vibration-Induced Climbing of Drops," Phys. Rev. Lett, Vol. 99, pp. 144501-1-4. https://doi.org/10.1103/PhysRevLett.99.144501
  16. Matsumoto, T., Fujii, H., Ueda, T., Kamai, M. and Nogi, K., 2005, "Measurement of Surface Tension of Molten Copper Using the Free-fall Oscillating Drop Method," Meas. Sci. Technol, Vol. 16, pp. 432-437. https://doi.org/10.1088/0957-0233/16/2/014
  17. Yamakita, S., Matsui, Y. and Shiokawa, S., 1999, "New Method for Measurement of Contact Angle (Droplet Free Vibration Frequency Method)," Jpn. J. Appl. Phys, Vol. 38, pp. 3127-3130. https://doi.org/10.1143/JJAP.38.3127
  18. Makino, K. and Michiyosi, I., "The Behavior of a Water Droplet on Heated Surfaces," Int. J. Heat Transfer, Vol. 27, pp. 781-791.
  19. Wang, H. T., Wang, Zh. B., Huang, L. M., Mitra, A. and Yan Y. S., 2001, "Surface Patterned Porous Films by Convection-Assisted Dynamic Self-Assembly of Zeolite Nanoparticles," Langmuir, Vol. 17, pp. 2572-2574. https://doi.org/10.1021/la0102509
  20. Truskett, V. and Stebe, K. j., 2003, "Influence of Surfactants on an Evaporating Drop: Fluorescence Images and Particle Deposition Patterns," Langmuir, Vol. 19, pp. 8271-8279. https://doi.org/10.1021/la030049t
  21. Scriven, L. E. and Sternling, C. V., 1960, "The Marangoni Effects" Nature, Vol. 187, pp. 186-188. https://doi.org/10.1038/187186a0
  22. Hu, H. and Larson, R. G., 2006, "Marangoni Effect Reverses Coffee-Ring Depositions," J. Phys. Chem. B, Vol. 110, pp. 7090-7094. https://doi.org/10.1021/jp0609232
  23. Xu, X. F. and Luo, J. B., 2007, "Marangoni Flow in an Evaporating Water Droplet," Appl. Phys. Letter, Vol. 91, p. 124102. https://doi.org/10.1063/1.2789402
  24. Oh, J. M., Legendre, D. and Mugele, F., 2012, "Shaken not Stirred - On Internal Flow Patterns in Oscillating Sessile Drops," Europhysics Letters, Vol. 98, p. 34003. https://doi.org/10.1209/0295-5075/98/34003
  25. Lamb, H., 1932, Hydrodynamics, Cambridge Univ. Press, New York, p. 475.
  26. Kang, K. H., Lee, S. J., Lee, C. M. and Kang, I. S., 2004, "Quantitative Visualization of Flow Inside an Evaporating Droplet using the Ray Tracing Method," Meas. Sci. Technol., Vol. 15, pp. 1104-1112. https://doi.org/10.1088/0957-0233/15/6/009