Instability of a moving liquid sheet in the presence of acoustic forcing

Mulmule, Aditya; Tirumkudulu, Mahesh S.; Ramamurthi, K.

doi:10.1063/1.3290745

Cited by 28 publications

(26 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The liquid sheet finally reaches a stable but smaller size and continues to flap in response to the acoustics ( figure 5(i)). These images appear similar to those of Mulmule et al (2010) where the entire liquid sheet is subject to external acoustic waves and those of Bremond et al (2007) where undulations were produced by head-on impingement of a single laminar jet on a vibrating impactor.…”

Section: Thickness Distribution Of a Liquid Sheet With Acoustic Forcingsupporting

confidence: 54%

“…The schematic diagram of the experimental setup is shown in figure 2 and is similar to that reported earlier (Mulmule et al 2010). Two identical converging nozzles made up of borosilicate glass with an exit diameter of 1.62 mm and of length 12 cm are used in the present experiments to obtain liquid sheets over a range of Weber numbers (W e d = 300 − 1000).…”

Section: Basic Principle Of the Laser Induced Fluorescence (Lif) Techmentioning

confidence: 72%

See 1 more Smart Citation

Stability of a moving radial liquid sheet: experiments

2015

Self Cite

View full text Add to dashboard Cite

A recent theory [Tirumkudulu & Paramati, "Stability of a moving radial liquid sheet: Time dependent equations.", Phys. of Fluids, 102107, 25, 2013] for a radially expanding liquid sheet that accounts for liquid inertia, interfacial tension and thinning of the liquid sheet while ignoring inertia of surrounding gas and viscous effects shows that such a sheet is convectively unstable at all frequencies and Weber numbers (W e ≡ ρ l U 2 h/σ) to small sinuous disturbances. Here, ρ l and σ are the density and surface tension of the liquid, respectively, U is the speed of the liquid jet, and h is the local sheet thickness. In this study, we use a simple non-contact optical technique based on laser induced fluorescence to measure the instantaneous local sheet thickness and its displacement of a circular sheet produced by head on impingement of two laminar jets. When the impingement point is disturbed via acoustic forcing, sinuous waves produced close to the impingement point travel radially outward. The phase speed of the sinuous wave decreases while the amplitude grows as they propagate radially outwards. Our experimental technique was unable to detect thickness variations in the presence of forcing suggesting that the variations could be smaller than the resolution of our experimental technique. The measured phase speed of the sinuous wave envelope matches with predictions while there is a qualitative agreement in case of spatial growth. We show that there is a range of frequencies over which the sheet is unstable due to both aerodynamic interaction and thinning effects while outside this range, thinning effects dominate. These results imply that a full theory that describes the dynamics of a radially expanding liquid sheet should account for both effects.

show abstract

Section: Thickness Distribution Of a Liquid Sheet With Acoustic Forcingsupporting

confidence: 54%

Section: Basic Principle Of the Laser Induced Fluorescence (Lif) Techmentioning

confidence: 72%

Stability of a moving radial liquid sheet: experiments

2015

Self Cite

View full text Add to dashboard Cite

show abstract

“…Second, radial liquid sheets forced by external acoustics waves also demonstrate similar behavior. 16 Finally, Clarke et al 17 show that sinusoidal perturbation of the 2D liquid curtain close to its source, resulted in a sinusoidal response at the same frequency at all points downstream from the source of perturbation. Further, these observations were in close agreement with the predictions of the linear time-dependent equations for 2D flow of Weinstein et al 15 which are similar to that derived here for the radially expanding sheet.…”

Section: Resultsmentioning

confidence: 97%

Stability of a moving radial liquid sheet: Time-dependent equations

Tirumkudulu

Paramati

2013

Physics of Fluids

Self Cite

View full text Add to dashboard Cite

We study the stability of a radial liquid sheet produced by head-on impingement of two equal laminar liquid jets. Linear stability equations are derived from the inviscid flow equations for a radially expanding sheet that govern the time-dependent evolution of the two liquid interfaces. The analysis accounts for the varying liquid sheet thickness while the inertial effects due to the surrounding gas phase are ignored. The analysis results in stability equations for the sinuous and the varicose modes of sheet deformation that are decoupled at the lowest order of approximation. When the sheet is excited at a fixed frequency, a small sinuous displacement introduced at the point of impingement grows as it is convected downstream suggesting that the sheet is unstable at all Weber numbers (We ≡ ρlU2h/σ) in the absence of the gas phase. Here, ρl is the density of the liquid, U is the speed of the liquid jet, h is the local sheet thickness, and σ is the surface tension. The sinuous disturbance diverges at We = 2 which sets the size of the sheet, in agreement with the results of Taylor [“The dynamics of thin sheets of fluid. III. Disintegration of fluid sheets,” Proc. R. Soc. London, Ser. A 253, 313 (1959)]. Asymptotic analysis of the sinuous mode for all frequencies shows that the disturbance amplitude diverges inversely with the distance from the edge of the sheet. The varicose waves, on the other hand, are neutrally stable at all frequencies and are convected at the speed of the liquid jet.

show abstract

“…Experiments on head-on jet impingement show that the sheet responds to the acoustic forcing at a certain minimum sound pressure level, and this minimum sound pressure level increases with increase in the excitation frequency (Mulmule, Tirumkudulu & Ramamurthi 2010). The sheet diameter and the drop size were also found to decrease in the presence of acoustic excitation (Mulmule et al.…”

Section: Introductionmentioning

confidence: 99%

Atomization of acoustically forced liquid sheets

Dighe

Gadgil

2019

J. Fluid Mech.

View full text Add to dashboard Cite

Atomization of a smooth laminar liquid sheet produced by the oblique impingement of two liquid jets and subjected to transverse acoustic forcing in quiescent ambient is investigated. The acoustic forcing perturbs the liquid sheet perpendicular to its plane, thereby setting up a train of sinuous waves propagating radially outwards from the impingement point. These sheet undulations grow as the wave speed decreases towards the edge of the sheet and the sheet characteristics, like intact length and mean drop size, reduce drastically as compared to the natural breakup. Our observations show that the effect of the acoustic field is perceptible over a continuous range of forcing frequencies. Beyond a certain forcing frequency, called the cutoff frequency, the effect of the external acoustic field ceases. The cutoff frequency is found to be an increasing function of the Weber number. Our measurements of the characteristics of spatially amplifying sinuous waves show that the instabilities responsible for the natural sheet breakup augment in the presence of external forcing. Combining the experimental observations and measurements, we conclude that the linear theory of aerodynamic interaction (Squire’s theory) (Squire, Brit. J. Appl. Phys., vol. 4 (6), 1953, pp. 167–169) predicts the important features of this phenomenon reasonably well.

show abstract

Instability of a moving liquid sheet in the presence of acoustic forcing

Cited by 28 publications

References 15 publications

Stability of a moving radial liquid sheet: experiments

Stability of a moving radial liquid sheet: experiments

Stability of a moving radial liquid sheet: Time-dependent equations

Atomization of acoustically forced liquid sheets

Contact Info

Product

Resources

About