Dual-Mode Linear Analysis of Temporal Instability for Power-Law Liquid Sheet

Deng, Hanyu; Feng, Feng; Wu, Xiaosong

doi:10.1615/atomizspr.2015012267

Cited by 3 publications

(4 citation statements)

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“…Also, Ma (2000) and Marchione et al (2007) concluded that the turbulence and unsteadiness in the internal flowfield is the main reason influencing the properties of the sheet formed at the orifice exit and the dynamics of the spray. This behaviour, though, contradicts numerical findings of Deng et al (2016).…”

Section: Liquid Discharge Sheet Formation and Primary Breakupcontrasting

confidence: 50%

Air–liquid interactions in a pressure-swirl spray

Jedelský

Malý

Corral

et al. 2018

International Journal of Heat and Mass Transfer

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The energy transfer between a liquid hollow cone spray and the surrounding air has been studied using both imaging and phase-Doppler techniques. The spray was produced by a pressure-swirl atomizer discharging Jet A-1 fuel at inlet over pressures of p = 0.5, 1.0 and 1.5 MPa into quiescent ambient air. The liquid exits the nozzle as a conical film which thins as it spreads and develops long-and shortwave sinusoidal instabilities with breakup occurring, at the length smaller than that predicted by the inviscid model, to form film fragments and ultimately droplets downstream the spray. The single shot imaging characterised the spray regions of near-nozzle flow, the breakup processes and the developed spray. The phase-Doppler system resolved the three components of velocity and size for the droplet flow as measured on radial profiles for four axial distances from the nozzle exit. A Stokes number, Stk, analysis of the droplets' response times to the airflow timescales showed that droplets < 5 µm followed the airflow faithfully and so were used to estimate the local airflow velocity. This allowed a comparison of both the droplet and airflow fields in terms of their mean and fluctuating velocity components to be made. The formation of the hollow cone spray and the interaction of the fragments and droplets with the air, through viscous drag, induce complex entrained airflows. The airflow was found to be highly anisotropic, fluctuating preferentially in the downstream direction, and spatially varying within three distinct spray regions. The air drag establishes a positive size-velocity correlation of droplets; their Stk reduces with axial distance and increases with droplet size and p; so that Stk ≈ 1 for 20-40 µm droplets and the largest droplets (80-160 µm, Stk > 10) move ballistically. The spatially resolved mean and turbulent kinetic energies of the air and spectra of the droplet velocity fluctuations are detailed in the paper. These findings are relevant to scientists and engineers modelling the complex two-phase flows.

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Section: Liquid Discharge Sheet Formation and Primary Breakupcontrasting

confidence: 50%

Air–liquid interactions in a pressure-swirl spray

Jedelský

Malý

Corral

et al. 2018

International Journal of Heat and Mass Transfer

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“…Therefore, ln(η b /η 0 ) cannot be obtained by the above analysis and is considered as an empirical constant. Researchers have made great efforts on this parameter, such as Deng [21], Weber [24], Dombrowski [25], Kroesser [26] and Kim [27]. Weber [24] pointed out that this parameter could be fixed at the value of 12 in their study range.…”

Section: Resultsmentioning

confidence: 99%

“…In order to validate our work, the comparison between Deng's experiment data [21] and theoretical prediction curves are shown in Here n is set to be smaller than 1, indicating that shear-thinning power-law fluid is used in the study.…”

Section: Resultsmentioning

confidence: 99%

“…Besides, in the actual flow condition of a plane liquid jet, the scale of the disturbance and the jet velocity in the y-axis is very small. So the shear stress τ xy and normal stress τ yy in the y-axis are neglected as reported by Xia et al [20], Deng et al [21] and Chang et al [22]. Then the momentum equations of liquid phase become:…”

Section: Instability Analysismentioning

confidence: 99%

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Effects of Asymmetric Gas Distribution on the Instability of a Plane Power-Law Liquid Jet

Guo

Wang²,

Bai

et al. 2018

Energies

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As a kind of non-Newtonian fluid with special rheological features, the study of the breakup of power-law liquid jets has drawn more interest due to its extensive engineering applications. This paper investigated the effect of gas media confinement and asymmetry on the instability of power-law plane jets by linear instability analysis. The gas asymmetric conditions mainly result from unequal gas media thickness and aerodynamic forces on both sides of a liquid jet. The results show a limited gas space will strengthen the interaction between gas and liquid and destabilize the power-law liquid jet. Power-law fluid is easier to disintegrate into droplets in asymmetric gas medium than that in the symmetric case. The aerodynamic asymmetry destabilizes para-sinuous mode, whereas stabilizes para-varicose mode. For a large Weber number, the aerodynamic asymmetry plays a more significant role on jet instability compared with boundary asymmetry. The para-sinuous mode is always responsible for the jet breakup in the asymmetric gas media. With a larger gas density or higher liquid velocity, the aerodynamic asymmetry could dramatically promote liquid disintegration. Finally, the influence of two asymmetry distributions on the unstable range was analyzed and the critical curves were obtained to distinguish unstable regimes and stable regimes.

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Instability breakup model of power-law fuel annular jets in slight multiple airflows

et al. 2020

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In this paper, a temporal instability model has been derived to explore the influence of slight multiple airflow movements for the power-law fuel annular jet. Adopting the method of linear approximation and considering two different disturbance modes, the power-law fuel jet dispersion equation has been obtained based on the initial and boundary conditions. The influence of dimensionless characteristic parameters for the annular jet is investigated. By solving the dispersion equation, it can be found that the para-sinuous mode is more likely to play a leading role. For low-speed cases, the outer crossflow gas promotes the instability of fuel annular jets more effectively, while the inner coaxial airflow has an obvious promotion impact on high-speed jets. Reducing the thickness of the fuel annular film will weaken the stable inertia of the fuel, make the fuel annular jet easier to break up, and enhance the primary breakup scale. Furthermore, increasing the outer or inner gas density can accelerate the annular spray breakup process, and also amplify the gain effect of airflows. Besides, pseudoplastic fluid annular jets are more unstable and more suitable as fuel for future use. These discussions aim for a better understanding of the power-law fuel annular jet breakup process with multiple airflows and provide theoretical guidance for practical applications.

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Dual-Mode Linear Analysis of Temporal Instability for Power-Law Liquid Sheet

Cited by 3 publications

References 0 publications

Air–liquid interactions in a pressure-swirl spray

Air–liquid interactions in a pressure-swirl spray

Effects of Asymmetric Gas Distribution on the Instability of a Plane Power-Law Liquid Jet

Instability breakup model of power-law fuel annular jets in slight multiple airflows

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