10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Capillary Oscillations in the Transient Mode of Flow Focusing: Comparison Between Experimental Measurements and Numerical Results
VICTORIEN MAMET, Michel Matton, Stéphane Gasser, Patrick Namy, Jean-Marc Dedulle, LMGP - Grenoble INP / UGA, DBV Technologies
Abstract Number: 361 Working Group: Aerosol Physics
Abstract Among droplet generation technologies, the flow focusing technique is a major process due to its control, stability, reproducibility and adaptability to the biomaterial handling. The principle is to create a spray from the coflowing of two fluids. In the transient flow, there is a oscillation of the liquid motion which has proved to be periodic. It has first been studied in the 1990s experimentally [1], and new phenomena inherent to the physical dynamics of the fluid flows have been found by numerical modeling.
We perform a series of experiments to study the transient mode in flow focusing, more particularly the behavior of the period of oscillation τ=T/T_0 versus the Reynolds number Re_l. We then compare it to the results of numerical simulations, performed on a model developed in [2] in order to give more range to our results.
The experiments are conducted with a custom made flow focusing device and measurement tools adapted for the range of the observations wanted.
The experiments show that during one period the liquid flow is subjected to several micro-oscillations called capillary oscillation during the oscillation, as predicted in numerical simulations. We find a step-like decreasing behavior for the dimensionless period versus the liquid Reynolds number. The behavior of the capillary oscillation number depending on this Reynolds number is in excellent correlation with the numerical results.
These results highlight the discontinuous response of the fluid flow depending on slight variations of the physical parameters and may allow to give some indicator of the flow regime.
[1] Gañán-Calvo, A. M. (1998). Generation of steady liquid microthreads and micron-sized monodisperse sprays in gas streams. Physical Review Letters, 80(2), 285.
[2] Mamet, V., Namy, P., & Dedulle, J. M. (2017). Numerical modeling of flow focusing: Quantitative characterization of the flow regimes. Physics of Fluids, 29(9), 093606.