Shock induced aerobreakup of a droplet

Sharma, Shubham; Singh, Awanish Pratap; Rao, S. Srinivasa; Kumar, Aloke; Basu, Saptarshi

doi:10.1017/jfm.2021.860

Cited by 66 publications

(89 citation statements)

References 63 publications

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“…Some models have proposed a mechanistic view of the breakup where it is assumed that surface instabilities play a major role in the atomization of droplets, particularly at high We. The 'Rayleigh-Taylor piercing' mechanism describes the rapid breakup of a flattened droplet by the penetration of surface waves generated on the windward face of the droplet due to rapid acceleration (Joseph, Beavers & Funada 2002;Theofanous & Li 2008;Sharma et al 2021). The Rayleigh-Taylor piercing mechanism has also been used to describe the breakup at low We, where it has been claimed to be the cause of the bag formation; however, recent works have called this into question, showing that the deformation rate is more strongly correlated to the breakup morphology and sizes at low We (Jackiw & Ashgriz 2021).…”

Section: Introductionmentioning

confidence: 99%

Prediction of the droplet size distribution in aerodynamic droplet breakup

Jackiw

2022

J. Fluid Mech.

125

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The rim and bag dynamics in aerodynamic droplet breakup are investigated experimentally and theoretically. Three main modes contribute to the breakup sizes in aerodynamic droplet breakup: the rim node, the remaining rim and the bag breakup modes. However, existing models only consider one mode and are, therefore, unable to predict the size distribution. The present theoretical work seeks to model the dominant breakup mechanisms of each mode and to relate these mechanisms to the size distribution. It is shown that the nodes can be modelled using either the Rayleigh–Taylor or Rayleigh–Plateau instabilities with comparable results and that the variation in the node sizes results from the variation in the amount of mass in the rim that flows into the node prior to the rim breakup. The breakup of the rim is shown to be a result of a combination of the Rayleigh–Plateau instability and a newly proposed collision mechanism, wherein the impact of the corrugated receding rim of the bag with the main rim forces the main rim to break with the same wavelength as the receding rim. The resulting size distribution of the droplet breakup is estimated assuming that the relative weighting of the breakup mechanisms for each mode follows a two-parameter gamma distribution. The volume of each geometry is used to estimate the volume weighting of the modes, giving a reasonable prediction of the size distribution resulting from aerodynamic droplet breakup.

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Section: Introductionmentioning

confidence: 99%

Prediction of the droplet size distribution in aerodynamic droplet breakup

Jackiw

2022

J. Fluid Mech.

125

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“…From (B2), we can obtain λ KH,1 < 0.1 mm in our experiment, indicating the possibility of the shear instability wave in the droplet length scale. Although the predicted wavelength of shear instability based on the KH limit underestimates the actual wavelength in many studies (Jalaal & Mehravaran 2014;Sharma et al 2021), we can still assume λ KH,1 d 0 based on the experimental observations, as shown in figure 6(a). The small-scale shear instability waves tend to cause local peeling on the droplet surface, or merge into a large liquid tongue.…”

Section: Discussionmentioning

confidence: 93%

“…2012; Jalaal & Mehravaran 2014; Sharma et al. 2021), especially those based on shock tube experiments, indicated that the early sheet originated from the KH instability wave on the surface of the droplet. The KH instability wave caused by the shear layer on the droplet surface was further stretched to form the sheet under the airflow action.…”

Section: Resultsmentioning

confidence: 99%

Droplet breakup in airflow with strong shear effect

Wang

Che

2022

J. Fluid Mech.

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The deformation and breakup of droplets in airflows is important in spray and atomisation processes, but the shear effect in non-uniform airflow is rarely reported. In this study, the deformation and breakup of droplets in a shear flow of air is investigated experimentally using high-speed imaging, digital image processing and particle image velocimetry. The results show that in airflow with a strong shear effect, the droplet breakup exhibits unique features due to the uplift and stretching produced by the interaction between the deformed droplet and the shear layer. The breakup process can be divided into three stages according to the droplet morphology and the breakup mechanism, namely the sheet breakup, the swing breakup and the rim breakup stages. Theoretical analysis reveals that the swing breakup is governed by the transverse Rayleigh–Taylor instability. A regime map of the droplet breakup is produced, and the transitions between different regimes are obtained theoretically. The stretching liquid film during the droplet deformation and the fragment size distribution after droplet breakup are analysed quantitatively, and the results show that they are determined by the competition of breakup at different stages affected by the shear. Finally, the effect of the droplet viscosity is investigated, and the viscosity inhibits the droplet breakup in a strong shear airflow.

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“…Understanding the physics of aerobreakup is crucial in designing and controlling these processes. Significant research has been already done to study the aerobreakup of Newtonian droplets, and they are well-reviewed in literature [5][6][7][8][9] . It is well established that the two most important dimensionless groups in the study of Newtonian droplet aerobreakup are Weber number (We) and Ohnesorge number (Oh), defined as…”

Section: Introductionmentioning

confidence: 99%

“…Advancements in experimental facilities like high-speed cameras with better resolution, pulsed laser with nanosecond accuracy and Laser-induced fluorescence imaging technique etc. re-ignited the research in the field of aerobreakup 9,23 . The possibility of unifying Newtonian and non-Newtonian breakup modes under a single roof has been explored 21 .…”

Section: Introductionmentioning

confidence: 99%

Shock induced aerobreakup of a polymeric droplet

Chandra¹,

Sharma²,

Basu³

et al. 2022

Preprint

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Droplet atomization through aerobreakup is omnipresent in various natural and industrial processes. Atomization of Newtonian droplets is a well-studied area; however, non-Newtonian droplets have received less attention despite their frequent encounters. By subjecting polymeric droplets of different concentration to the induced airflow behind a moving shock wave, we explore the role of elasticity in modulating the aerobreakup of viscoelastic droplets. Three distinct modes of aerobreakup are identified for a wide range of Weber number (∼ 10 2 − 10 4 ) and Elasticity number (∼ 10 −4 − 10 2 ) variation; these modes are-vibrational, shear-induced entrainment and catastrophic breakup mode. Each mode is described as a three stage process. Stage-I is the droplet deformation, stage-II is the appearance and growth of hydrodynamic instabilities, and stage-III is the evolution of liquid mass morphology. It is observed that elasticity plays an insignificant role in the first two stages, but a dominant role in the final stage. The results are described with the support of adequate mathematical analysis.

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Shock induced aerobreakup of a droplet

Cited by 66 publications

References 63 publications

Prediction of the droplet size distribution in aerodynamic droplet breakup

Prediction of the droplet size distribution in aerodynamic droplet breakup

Droplet breakup in airflow with strong shear effect

Shock induced aerobreakup of a polymeric droplet

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