Particle and droplet clustering in oscillatory vortical flows

Y. Dagan, D. Katoshevski, J. B. Greenberg

    Research output: Contribution to journalArticlepeer-review

    5 Scopus citations

    Abstract

    A new mathematical analysis of particle and droplet clustering in a fluctuating vortex flow is presented. Twodimensional particle and droplet dynamics equations are solved numerically and analytically, assuming an oscillating vortex flow field. Droplet grouping was found to occur in the vicinity of an oscillating vortex and new streak-like grouping patterns of droplets in a vortex are disclosed. The combination of circumferential and radial fluctuations produces the most significant effects on the droplet grouping, facilitating the construction and destruction of the streak patterns, depending on the chosen flow field and droplet properties. A new analytical formulation is derived using perturbation analyses to model the swirl fluctuations on the spray, providing a simple method to evaluate the effect of droplet dispersion and droplet clustering under fluctuating vortex flows. This approach was found to be in good agreement with the numerical results in cases of low Stokes numbers for both evaporating and nonevaporating droplets. It is shown that evaporation tends to increase the droplet fluctuation amplitude with time and therefore intensifies the grouping effect. The combination of oscillation and evaporation was found to have the most significant effect on droplet grouping, where the amplitude of the proximity curve rapidly increases in a nonlinear manner. Despite the simplicity of the current model its predictions provide insight into the driving mechanisms behind the much more complex turbulent spray-combustion regime, in which similar droplet grouping patterns occur.

    Original languageEnglish
    Pages (from-to)629-643
    Number of pages15
    JournalAtomization and Sprays
    Volume27
    Issue number7
    DOIs
    StatePublished - 1 Jan 2017

    Keywords

    • Droplet clustering
    • Spray dynamics
    • Vortex flows

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