Droplet grouping is important in technical applications and in nature where more than one droplet is seen. Despite its relevance for such problems, the fundamentals of the grouping processes are not yet fully understood. Initial conditions that expedite or impede the formation of droplet groups have been studied, but a thorough investigation of the temporal and spatial evolution of the forces at play has not been conducted. In this work, the grouping process in monodisperse droplet streams is examined in detail by direct numerical simulation (DNS), for the first time, using the multiphase code Free Surface 3D. The code framework is based on the volume-of-fluid method and uses the piecewise linear interface calculation method to reconstruct the interface. A method is established to quantify the development and evolving differences of pressure and shear drag forces on each droplet in the stream using the available DNS data. The results show a linear increase in the difference between the forces, where the drag force on the leading droplet is always larger than that on the trailing droplet. A comprehensive parametric study reveals that, on the one hand, large initial inter-droplet separation and small group distances increase grouping time due to reduced difference in the drag coefficients. On the other hand, higher initial Reynolds numbers and larger irregularities in the geometrical arrangement promote droplet grouping. The flow field shows stable wake structures at initial Reynolds numbers of 300 and the onset of vortex shedding at Reynolds numbers of 500, affecting the next pair of droplets, even for larger separation distances.
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August 2022
Research Article|
August 11 2022
Investigation of droplet grouping in monodisperse streams by direct numerical simulations
M. Ibach
;
M. Ibach
a)
(Conceptualization, Data curation, Formal analysis, Investigation, Software, Validation, Visualization, Writing – original draft, Writing – review & editing)
1
Institute of Aerospace Thermodynamics (ITLR), University of Stuttgart
, Stuttgart, Germany
a)Author to whom correspondence should be addressed: matthias.ibach@itlr.uni-stuttgart.de
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V. Vaikuntanathan
;
V. Vaikuntanathan
(Conceptualization, Data curation, Formal analysis, Investigation, Validation, Writing – review & editing)
2
Department of Mechanical Engineering, Shiv Nadar University (SNU)
, Greater Noida 201314, Uttar Pradesh, India
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A. Arad
;
A. Arad
(Formal analysis, Investigation, Writing – review & editing)
3
Department of Civil and Environmental Engineering, Ben-Gurion University of the Negev (BGU)
, Beer-Sheva, Israel
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D. Katoshevski
;
D. Katoshevski
(Formal analysis, Funding acquisition, Investigation, Supervision, Writing – review & editing)
3
Department of Civil and Environmental Engineering, Ben-Gurion University of the Negev (BGU)
, Beer-Sheva, Israel
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J. B. Greenberg
;
J. B. Greenberg
(Formal analysis, Funding acquisition, Investigation, Supervision, Writing – review & editing)
4
Faculty of Aerospace Engineering, Technion—Israel Institute of Technology (IIT)
, Haifa, Israel
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B. Weigand
B. Weigand
(Conceptualization, Formal analysis, Funding acquisition, Investigation, Project administration, Resources, Supervision, Writing – review & editing)
1
Institute of Aerospace Thermodynamics (ITLR), University of Stuttgart
, Stuttgart, Germany
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a)Author to whom correspondence should be addressed: matthias.ibach@itlr.uni-stuttgart.de
Physics of Fluids 34, 083314 (2022)
Article history
Received:
April 29 2022
Accepted:
July 14 2022
Citation
M. Ibach, V. Vaikuntanathan, A. Arad, D. Katoshevski, J. B. Greenberg, B. Weigand; Investigation of droplet grouping in monodisperse streams by direct numerical simulations. Physics of Fluids 1 August 2022; 34 (8): 083314. https://doi.org/10.1063/5.0097551
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