Toward a Physical Characterization of Raindrop Collision Outcome Regimes
Open accessAbstract
A comprehensive raindrop collision outcome regime diagram that delineates the physical conditions associated with the outcome regimes (i.e., bounce, coalescence, and different breakup types) of binary raindrop collisions is proposed. The proposed diagram builds on a theoretical regime diagram defined in the phase space of collision Weber numbers We and the drop diameter ratio p by including critical angle of impact considerations. In this study, the theoretical regime diagram is first evaluated against a comprehensive dataset for drop collision experiments representative of raindrop collisions in nature. Subsequently, the theoretical regime diagram is modified to explicitly describe the dominant regimes of raindrop interactions in (We, p) by delineating the physical conditions necessary for the occurrence of distinct types of collision-induced breakup (neck/filament, sheet, disk, and crown breakups) based on critical angle of impact consideration. Crown breakup is a subtype of disk breakup for lower collision kinetic energy that presents distinctive morphology. Finally, the experimental results are analyzed in the context of the comprehensive collision regime diagram, and conditional probabilities that can be used in the parameterization of breakup kernels in stochastic models of raindrop dynamics are provided.
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In Testik's theory, ignoring viscous dissipation and impact parameter, α = β = 1 approximately for the bouncing-coalescence-separation transition; α < 1 for bouncing, α > 1 and β < 1 for coalescence, and β > 1 for separation.
“In Testik's theory, 26,48 by ignoring the effects of viscous dissipation and the impact parameter, α β = = 1 approximately for the bouncing-coalescence-separation transition, where the two energy ratios divide the We -Δ parameter space into three regimes, with α < 1 for bouncing, α > 1 and β < 1 for coalescence, and β > 1 for separation.”
From Droplet collision of hypergolic propellants (2024) · cites this paper as [48]
Testik et al. found that the theoretical model for bouncing and coalescence regimes still holds for off-center collisions, while neck separation occurred at large B in the coalescence regime.
“Testik et al.48 found that the theoretical model for the bouncing and coalescence regimes still holds for off-center collisions, while the so-called “neck separation” that occurred at large B was observed in the coalescence regime.”
From Droplet collision of hypergolic propellants (2024) · cites this paper as [48]
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- Authors
- Testik, F. Y., Barros, A. P., & Bliven, L. F.
- Affiliations
- Clemson University (US)
- Duke University (US)
- Wallops Flight Facility (US)
- Venue
- Journal of the Atmospheric Sciences
- Publisher
- American Meteorological Society
- Published
- 2011-04-01
- Volume
- 68
- Issue
- 5
- Pages
- 1097-1113
- ISSN
- 0022-4928 (ISSN-L)
- 1520-0469
- OpenAlex
- W2076321058
- Cited by
- 37
- References
- 43
- Citations by year
- 2026: 2 · 2025: 4 · 2024: 7 · 2023: 2 · 2022: 1 · 2021: 1 · 2020: 2 · 2019: 1 · 2018: 3 · 2017: 6 · 2015: 2 · 2014: 1 · 2013: 3 · 2012: 2
- FWCI
- 1.93
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- Journal of the Atmospheric Sciences (publishedVersion)
- NASA STI Repository (National Aeronautics and Space Administration) (submittedVersion)
- Funders
- National Science Foundation
- National Aeronautics and Space Administration
- Clemson University
- Topics
- Physical Sciences › Engineering › Computational Mechanics › Fluid Dynamics and Heat Transfer
- Physical Sciences › Earth and Planetary Sciences › Atmospheric Science › Precipitation Measurement and Analysis
- Physical Sciences › Environmental Science › Global and Planetary Change › Atmospheric aerosols and clouds
- Keywords
- Weber number, filament breakup, sheet breakup, bounce, coalescence
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