Abstract
The interaction between two falling droplets in the liquid–liquid two-phase flow has been investigated in detail with the aids of the index matching technique and PIV. It has been almost impossible to measure or even visualize the multiple phases simultaneously. This is because of the difference in the refractive indices of each phase. In this study, the refractive index of the water phase has been equalized to that of the oil phase by adjusting the concentration of the aqueous solution of glycerol and thus the simultaneous visualization of both phases and also the PIV measurement have been carried out. Presently, the interaction between two falling droplets has been intensively investigated. The interaction between two solid particles has been well known by the name of drafting–kissing–tumbling (DKT) motion. Similar motion to DKT is also observed for the droplets, which are found not to really kiss. It is found that the flows inside of the droplets are also affected by the interaction between two droplets while one droplet overtakes the other. The conditions for the initial relative positions of the two droplets to overtake have been summarized. It has been made clear that the chasing droplet is pulled by the wake of the preceding droplet.
Graphical abstract
Similar content being viewed by others
References
Cieslinski JT, Polewski J, Szymczyk JA (2005) Flow field around growing and rising vapour bubble by PIV measurement. J Vis 8(3):209–216
Clift R, Grace JR, Weber ME (1978) Bubbles, drops and particles. Academic Press, New York
Dandy DS, Leal LG (1989) Buoyancy-driven motion of a deformable drop through a quiescent liquid at intermediate Reynolds numbers. J Fluid Mech 208:161–192
Fortes AF, Joseph DD, Lundgren TS (1987) Nonlinear mechanics of fluidization of beds of spherical particles. J Fluid Mech 177:467–483
Kitagawa A, Sugiyama K, Murai Y (2004) Experimental detection of bubble-bubble interactions in a wall-sliding bubble swarm. Int J Multiph Flow 30(10):1213–1234
Knapp Y, Bertrand E (2005) Particle imaging velocimetry measurements in a heart simulator. J Vis 8(3):217–224
Murai Y, Qu J, Yamamoto F (2006) Three-dimensional interaction of bubbles at intermediate Reynolds numbers. Multiph Sci Technol 18(2):175–197
Ninomiya N, Yasuda K (2006) Visualization and PIV measurement of the flow around and inside of a falling droplet. J Vis 9(3):257–264
Yamauchi M, Uemura T, Ozawa M (2000) Velocity distributions inside and outside of a water drop in oil. Application of laser techniques to fluid mechanics, CD-ROM, pp 1–6
Acknowledgements
The authors greatly acknowledge the experimental support by Mr. Takeshi Mori and Mr. Kenta Sato of the Graduate School of Engineering of Utsunomiya University.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Ninomiya, N., Tsukada, S., Ikeda, M. et al. Interaction between two falling droplets in the liquid–liquid two-phase flow. J Vis 21, 1009–1016 (2018). https://doi.org/10.1007/s12650-018-0509-z
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s12650-018-0509-z