Atomization: Break-up of thin liquid sheets

The process of atomization, which involves the break-up of a mass of liquid into tiny droplets, plays an important role in many industrial applications such as spray combustion, spray painting, agricultural sprays, ink jet printing, and powdered milk processing to name a few. One of the main objectives of the atomization process is to control the drop size distribution so as to achieve the desired process efficiently. While the break-up of liquid into droplets is a complex process involving turbulent flows and highly deformed interfaces, much of the effort has focused on the initial process of break-up where linear theories can be used to obtain a first estimate of the droplet size distribution. The proposed work focuses on the atomization of thin liquid sheets, such as those produced from fan spray nozzles, to predict the growth of disturbances that lead to the eventual break-up of liquid sheets.

Much of previous work has identified the cause of the break-up of liquid sheets to be the aerodynamic interactions of the liquid sheet with the surrounding gas phase. However, recent work from our group has shown that the liquid sheets formed either by impingement of laminar liquid jets or via fan-spray nozzles are susceptible to break-up even in the absence of aerodynamic interactions [Tirumkudulu & Paramati (2013); Paramati et al (2015); Majumdar & Tiurmkudulu (2016)] due to the spatial variations in the film thickness. Further, the growth rates predicted by a theory that accounts for the spatial variation of film thickness but ignores the gas phase are remarkably close to the measurements over a range of forcing frequencies and amplitudes even though the experiments were performed in the presence of a surrounding gas phase. This is in contrast to large discrepancies observed when the same measurements were compared with the predictions of a spatial stability analysis for a moving liquid sheet that accounts for the inertia of the surrounding gas phase but ignores the thickness variation of the sheet [Crapper et al (1975); Bremond et al (2007)].

The goal of the project is to investigate via experiments, theory and simulations, the break-up of liquid sheet at varying ambient pressures so as to ascertain the contribution of the aerodynamic interactions and the spatial variation of thickness on the sheet break-up and drop size distribution.

References:

Bremond, N, Clanet, C and Villermaux, E., “Atomization of undulating liquid sheets.”, J Fluid Mech, 585, pp 421-456, 2007

Crapper, G. D. Dombrowski, N. and Pyott, G. A. D., “Large amplitude Kelvin-Helmholtz waves on thin liquid sheet,” Proc. R. Soc. London, Ser. A 342(1629), 209–224 (1975).

Majumdar N and Tirumkudulu MS, “Growth of Sinuous Waves on thin liquid sheets: Comparison of predictions with experiments ", Phys Fluids, 28(5), 052101 (2016)

Paramati, M., Tirumkudulu, M.S., and Schmid, P., “Stability of a moving radial liquid sheet: Experiments", J Fluid Mech, 770, 398 (2015)

Tirumkudulu, M.S., and Paramati, M., “Stability of a moving radial liquid sheet: Time-dependent equations", Phys. Fluids, 25(10), (2013)

Proposing Faculty
Research Area
  • Coatings
  • Computational Flow Modelling (CFD)
  • Fluid Mechanics and Stability