Impulsive generation of jets by flow focusing

Gordillo, José Manuel; Onuki, Hajime; Tagawa, Yoshiyuki

doi:10.1017/jfm.2020.270

Cited by 23 publications

(39 citation statements)

References 21 publications

(44 reference statements)

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“…Typically, is of the order of 2 for small contact angles as set in our experiments. Recently, a detailed theoretical analysis of the flow focusing effect can be found in Gordillo et al (2020) who report a quantitative agreement with experimental results using the impact-and lasedinduced ejection techniques. The cavitation bubble and jet ejection behaviour are simultaneously captured using two fast cameras at 50000 fps (Photron SA-X2) and 30000 fps (Photron SA-X), respectively.…”

Section: Focused Jet Generationmentioning

confidence: 64%

“…The deformation of the interface leads to a thin stream of liquid with a conical (focused) shape propagating through the air. This well known phenomenon occurs due to a flow focusing mechanism of the velocity and impulsive pressure fields (Antkowiak et al 2007;Gordillo et al 2020). Focused jets typically appear in the bursting of bubbles at liquid interfaces (Duchemin et al 2002;Longuet-Higgins 1983), high amplitude Faraday waves (Goodridge et al 1999;Longuet-Higgins 2001), or the ubiquitous collapse of cavities after a drop impact on a liquid interface (Worthington and Cole 1897;Fedorchenko and Wang 2004).…”

Section: Introductionmentioning

confidence: 99%

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Effect of liquid elasticity on the behaviour of high-speed focused jets

et al. 2021

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We investigate the effect of highly contrasting non-Newtonian liquid properties on the formation of liquid jets with a focused shape. By using two nozzle-free ejection techniques, mechanically impact- and laser-induced, fast jets of a highly elastic (sodium polyacrylate) and weakly elastic (xanthan-gum) diluted polymer solutions are generated. A unique high-speed effect is encountered at the jet ejection onset of the highly elastic solution. Its jet-tip speed is on average 1.4 times faster in comparison to a Newtonian (glycerin/water) and the weakly elastic liquids. We explain this effect occurring as a result of the high viscoelasticity of the sodium polyacrylate solution. Additionally, a ‘bungee jumper’ jet behaviour (Morrison and Harlen in Rheol Acta 49(6):619–632, 2010) is observed in a regime of high speed ($$10<V_j<40$$ 10 < V j < 40 m/s) and high viscosity ($$\mu >20$$ μ > 20 mPa s) not previously examined. We additionally characterise the viscoelastic non-breakup jet limit using the Bazilevskii et al. (Fluid Dyn 40(3):376–392, 2005) ejection criterion. Herein, the extensional rheological parameters are measured implementing a novel DoS-CaBER technique (Dinic et al. in Lab Chip 17(3):460–473, 2017). Our findings may influence results of inkjet printing technologies and recent nozzle-free ejection systems for ejecting liquids with non-Newtonian properties. Graphical abstract

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Section: Focused Jet Generationmentioning

confidence: 64%

Section: Introductionmentioning

confidence: 99%

Effect of liquid elasticity on the behaviour of high-speed focused jets

et al. 2021

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“…From the literature, it is known that when a pressure wave propels a concave-shaped meniscus forward, a jet forms due to geometrical focusing of the flow at the meniscus due to an inhomogeneous pressure gradient field along the meniscus [42,43]. The pressure gradient and the resulting velocity are larger at the center of a concave meniscus than at its edge (see also Ref.…”

Section: Jet-formation Mechanismmentioning

confidence: 99%

“…The meniscus can also be destabilized at an intermediate Ohnesorge number by an inhomogeneous velocity field at the meniscus, due to the finite transport time of viscous-drag-induced vorticity from the wall to the center of the nozzle [40]. Furthermore, the meniscus can be deformed by geometrical-flow focusing when a pressure wave hits a concave meniscus [41][42][43]. Finally, meniscus destabilization and the resulting bubble pinch-off can originate from the interaction of capillary waves at the gas-liquid interface.…”

Section: Introductionmentioning

confidence: 99%

Meniscus Oscillations Driven by Flow Focusing Lead to Bubble Pinch-Off and Entrainment in a Piezoacoustic Inkjet Nozzle

et al. 2021

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The stability of high-end piezoacoustic drop-on-demand (DOD) inkjet printing is sometimes compromised by the entrainment of an air bubble inside the ink channel. Here, bubble pinch-off from an oscillating meniscus is studied in an optically transparent DOD printhead as a function of the driving waveform. We show that bubble pinch-off follows from low-amplitude high-frequency meniscus oscillations on top of the global high-amplitude low-frequency meniscus motion that drives droplet formation. In a certain window of control parameters, phase inversion between the low-and high-frequency components leads to the enclosure of an air cavity and bubble pinch-off. Although phenomenologically similar, bubble pinch-off is not a result of capillary-wave interaction such as observed in drop impact on a liquid pool. Instead, we reveal geometrical-flow focusing as the mechanism through which, at first, an outward jet is formed on the retracted concave meniscus. The subsequent high-frequency velocity oscillation acts on the now toroidal-shaped meniscus and it accelerates the toroidal ring outward, resulting in the formation of an air cavity that can pinch off. Through incompressible boundary-integral simulations, we reveal that bubble pinch-off requires an unbalance between the capillary and inertial time scales and that it does not require acoustics. The critical control parameters for pinch-off are the pulse timing and amplitude. To cure the bubble entrainment problem, the threshold for bubble pinch-off can be increased by suppressing the highfrequency driving through appropriate waveform design. The present work therefore aids the improvement of the stability of inkjet printers through a physical understanding of meniscus instabilities.

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“…We set l top = 30 mm, l bottom = 0.30, 0.43, 0.60, 1.0, 5.0, 9.0 mm, r = 0.6 mm, R = 6.2 mm, similar to experimental values. Under each condition, the Laplace equation was solved to obtain the initial liquid velocity V. By substituting the initial velocity V and initial contact angle = 25 • into the following equation proposed by Gordillo et al (2020), the jet velocity V jet is…”

Section: Potential Flow Analysis and Renewed Jet Velocity Modelmentioning

confidence: 99%