Disintegration Of Liquid Jet Research Articles

Two-valued breakup length of a water jet issuing from a finite-length nozzle under normal gravity

Laboratory experiments are conducted in which water is issued vertically downward from a finite-length nozzle at a constant speed using a piston. The results of these experiments indicate that the breakup length of the liquid jet is two-valued at Weber numbers greater than unity but less than a certain value, which depends on the nozzle length-to-radius ratio and the Bond number. In addition to a long breakup length, which is consistent with the conventional observation, another shorter breakup length is realized at the same jet issue speed. Each experimental run for a specific jet issue speed begins from the start of liquid issue so that each run is independent of the other runs. Transition between the two breakup lengths seldom occurs in each run. Which of the two breakup lengths occurs is determined at the start of liquid issue, when the capillary wave produced by the liquid jet tip contraction easily reaches the nozzle exit. Unlike the conventional belief, which is based on the Plateau-Rayleigh instability theory, this experimental evidence demonstrates that liquid jet disintegration occurs in a deterministic manner. The previously proposed self-destabilizing mechanism of a liquid jet in microgravity, in which the origin of the unstable wave responsible for the breakups is attributed to the formation of an upstream propagating capillary wave at every breakup, is extended to explore the physics underlying the observed liquid jet disintegration behaviors.

Study of the effects of the injector length/diameter ratio on the surface properties of turbulent liquid jets in still air using X-ray imaging

The disintegration of turbulent liquid jets in gases, a process termed turbulent primary breakup, has many industrial applications, especially in liquid injection systems whose injector internal flow results in enhanced turbulence generation. An investigation was carried out by using X-ray diagnostics at the Advanced Photon Source (APS) facility of Argonne National Laboratory on two injectors with a smooth entry followed by round passage with different length-to-diameter ratios of 10 and 40, operating at the same injection speed. The test matrix was designed to eliminate cavitation and to isolate the effect of length/diameter ratio of the injector passage and to determine the importance of jet turbulence compared to aerodynamic forces. The X-ray diagnostics used allowed the surface and internal topography of liquid jets to be visualized and the spatial distribution of the surface ligaments to be revealed in the near-injector region. The present results show that the separation distance between a ligament and its neighbors depends on the ligament sizes, and the injector length/diameter ratio affects the rates of breakup.

Modeling the disintegration of modulated liquid jets using volume-of-fluid (VOF) methodology

In this study, we present the numerical investigations on the effect of finite velocity modulations imposed on an otherwise unperturbed cylindrical liquid jet issuing into stagnant gas. Sinusoidal velocity fluctuations of finite frequency and amplitude are imposed at the liquid jet inlet and the resulting liquid jet surface deformation is captured using a volume of fluid (VOF) methodology, utilizing compressive interface capturing scheme for arbitrary meshes (CICSAM) scheme. Variation of the simulation parameters, comprising of the mean liquid jet velocity, modulation amplitude and frequency grouped together using a set of non-dimensional parameters, leads to the formation of a wide gamut of reproducible liquid structures such as waves, upstream/downstream directed bells, chains of droplets similar to those observed in experiments. Elaborate tests on the effect of injection velocity and inlet jet diameter are investigated to characterize the breakup process. The computations efficiently capture the diverse flow structures generated by the evolving modulated liquid jet inclusive of several non-linear dynamics such as growth of surface waves, ligament interaction with shear vortices and its subsequent thinning process. The simulations identify the deterministic behavior of modulated liquid jets to predict liquid disintegration modes under given set of non-dimensional parameters.

Numerical simulation of the disintegration of forced liquid jets using volume-of-fluid method

The present numerical study investigates the effect of finite sinusoidal velocity modulations imposed on an otherwise unperturbed cylindrical liquid jet issuing into stagnant gas using Volume-of-Fluid (VOF) methodology. Variation of the simulation parameters, comprising of the mean liquid jet velocity, modulation amplitude and frequency grouped together using a set of non-dimensional parameters, leads to the formation of a wide gamut of reproducible liquid structures such as surface waves, upstream/downstream directed bells and chains of droplets similar to those observed in experiments. The computations efficiently capture the diverse flow structures generated by the evolving modulated liquid jet inclusive of several nonlinear dynamics such as growth of surface waves, ligament interaction with shear vortices and its subsequent thinning process. The simulations identify the deterministic behaviour of modulated liquid jets to predict liquid disintegration modes under given set of non-dimensional parameters.

Modeling the disintegration of cavitating turbulent liquid jets using a novel VOF–CIMD approach

In this article, a novel modeling approach capable of simultaneously tracking the events of cavitation, occurring within an injector nozzle, and the liquid jet breakup process, inclusive of spray formation, in the nozzle exterior is presented. A single fluid model, embedded with a Volume-of-Fluid (VOF)-based interface capturing methodology for monitoring the liquid–gas interface dynamics, is supplemented with a vapor transport model for predicting cavitation events triggered within the liquid. While the surface forces due to liquid–gas interfacial instabilities are modeled using a Continuum Surface Force model, a Cavitation-Induced-Momentum-Defect (CIMD) correction approach is employed to account for the effects of cavitation dynamics within the liquid flow. Liquid turbulence is modeled using the well-known RNG k–ε model inclusive of new source terms due to cavitation-induced turbulent kinetic energy production and dissipation. The combined VOF–CIMD methodology is validated by examining the effects of cavitation on the disintegration of turbulent planar liquid jets exiting a two-dimensional nozzle. Different flow Reynolds and Cavitation number configurations are tested. The results predicted by the model including those of the transport vapor dynamics and the liquid jet disintegration processes match, both qualitatively and quantitatively, very well with the available experimental data. In comparison with experimental observation, our model predicts different regimes of liquid jet behavior such as wavy jet, spray formation simultaneously with events of developing or super-cavitation. The numerical approach elaborated in this article can be extensively applied in the design and development of efficient spray applicators and other industrial fluidic devices.

噴射液の自己不安定化機構の理論的研究

Disintegration mechanism through a liquid-phase feedback loop is explored for a circular liquid jet issued into an otherwise quiescent gas. An asymptotic analysis of capillary waves radiating from the liquid jet tip is used to derive analytical expression for the feed back loop for the regular axisymmetric liquid jet disintegration occurring at a large distance from the nozzle exit for various Weber numbers. The calculation results predict the breakup characteristics which are consistent with the experimental observations. The role of turbulence contained in the issued jet and the change in atomization feature at large Weber numbers are also discussed briefly.

Modelling prediction of the microcapsule size of polyelectrolyte complexes produced by atomization

Abstract In order to have a better understanding of the atomization process for microencapsulation applications the disintegration of polymer liquid jets (sodium alginate) injected into high-velocity gas streams was studied and a mathematical model to predict the microparticle size has been developed. Air-blast atomization of viscous non-Newtonian fluid (alginate solution) was carried out in order to produce microbeads (1–50 μm) based on polyelectrolyte complexes with particle size control and a particle size distribution with a relative span factor, ( D 0.9 − D 0.1 )/ D 0.5 , less than 1.4. The accuracy of the wave-mechanisms-based models in predicting droplet size after breakup of alginate solution has been demonstrated. The atomized microparticle size were expressed in terms of three dimensionless groups, the liquid/air mass ratio, the Weber number and the Ohnesorge number in simple forms whose exponents and coefficients were determined by least-squares fit to the experimental data. With these data two semi-empirical models have been proposed to predict the particle size obtained from the microencapsulation. Both models allow the prediction of particle size of the microcapsules obtained by atomization processes.

Effect of the Cavitation in a Nozzle on the Liquid Breakup (3rd Report, Pressure Variation Inside 2D Nozzle)

The objective of this study is to promote disintegration of liquid jet by cavitation inside the nozzle. In this report, the effects of the pressure variartion inside 2-dimensional (2D) nozzle on behavior of liquid flow and the breakup of issuing liquid are investigated. When the nozzle length/ nozzle width ratio L/W value is large, the pressure inside nozzle decreases at the nozzle inlet, and increases before the middle section is reached, and any disturbance in the liquid flow inside the nozzle decreases in the vicinity of the outlet. When L/W value is small, the injection pressure increases, the pressure that decreased at the nozzle sharp corner part maintains negative pressure until the vicinity of the nozzle outlet. This trend prevents any disturbance due to the generation and disappearance of cavitation from attenuating.

A STATISTICAL MORPHOLOGICAL DETERMINATION OF THE GROWTH RATE OF THE INTERFACIAL DISTURBANCE OF AN EXCITED RAYLEIGH JET;

ABSTRACT : This article presents two different image processing techniques applied to a series of pictures of liquid jet disintegration. The first one is based on a mathematical morphological analysis. It extracts characteristics from the series which are linked to the growth rate of the jet disturbance thanks to a simple disintegration model. The second analysis shows the dynamics of the jet picture series thanks to the proper orthogonal decomposition applied to pictures. 1- Introduction The disintegration of a cylindrical liquid jet is studied in terms of a morphological characterization of the jet interface. As shown long ago by Lord Rayleigh (1879), the disintegration of the jet is governed by the growth rate of the disturbance. Numerous experimental studies on the stability of a liquid jet can be found in the literature. Recently, Adeline et al. (1999) have used a complex image analysis based on edge tracking and wavelet transform to determine experimentally the growth rate. In this paper, we present another way to determine the growth rate on an excited jet by a morphological analysis of the jet pictures. This analysis takes into account the length distribution of the vertical and horizontal lines that make up the two-level jet pictures. The interest of this original approach resides in its ability to provide statistical morphological information with a very simple image processing program. The next chapters will present the morphological analysis and its application to the Rayleigh jet. We will show that the principal hypothesis of the disintegration model is respected using a statistical filtering on the picture series given by the Proper Orthogonal Decomposition (POD).

Synergetic effects of secondary liquid drop impact and solid particle impact during hydro-abrasive erosion of brittle materials

The paper contains an analysis of the erosion capability of water drops formed during the acceleration of solid particles by a high-speed water jet. A dynamic fracture criterion for brittle materials is combined with stress equations for drop impact. Corresponding drop sizes are calculated with already existing relationships for liquid jet disintegration. Critical impact velocities are estimated for given drop diameters, and a fracture map is designed. Critical liquid jet velocities are rather low for soft rocks, such as limestone (92 m/s), and sandstone (200 m/s), but high for hard rocks, such as granite (1250 m/s) and basalt (1662 m/s).

Multiphase Flow Dynamics, Volume 1: Fundamentals; Volume 2: Thermal and Mechanical Interactions

Multiphase Flow Dynamics, Volume 1: Fundamentals; Volume 2: Thermal and Mechanical Interactions

Effect of the Cavitation in a Nozzle on the Liquid Breakup.

The objective of this study is to promote disintegration of liquid jet by cavitation inside the nozzle. Using cylindrical nozzle, the effects of the nozzle dimensions on the liquid breakup are investigated. When the length-diameter ratio L/D of the nozzle is low, cavitation bubbles are formed inside the nozzle and the breakup of the issuing jet is promoted.

Disintegration of Liquid Jets and Drop Drag Coefficients in Pressurized Nitrogen and Carbon Dioxide

The aim of this investigation is to clarify of the basic phenomena at the disintegration of liquid jets in a pressurized gas at up to 35 MPa. This is carried out by the characterization of the forces involved in the disintegration of liquid jets, which are influenced by the physical properties of the phases used.

Effects of conducting liquid jet disintegration on specific charge of spray

This paper is a study of the effects of jet instabilities on the current due to satellite charging compared to the main droplet current and the charge to mass ratio of highly conducting liquid. Two jet break up modes were investigated; the whipping mode of atomisation, using DC field, and the varicose mode of atomisation, employing an AC field superimposed on a DC field. For the whipping mode of instability, the experimental results have shown that the satellite current is two orders of magnitude higher than the main droplet current, while for the varicose mode, no satellite current is detected. The whipping mode of atomisation is a random phenomenon which produces polydispersed spray. It is, therefore, very difficult to apply the energy minimisation principle. However, in the case of the sausage mode of atomisation, the experimental results indicate that the energy minimisation approach pertaining to the disintegration of a charged liquid jet into uniform droplets is valid.

ONE-DIMENSIONAL SIMULATION OF THE BREAKUP OF CAPILLARY JETS OF CONDUCTING LIQUIDS. APPLICATION TO E.H.D. SPRAYING

Nonlinear breakup of charged liquid jets is numerically analyzed in this work in the limit of a very small electrical Strouhal number T e/ T b≪1 (i.e. negligible charge relaxation effects, applicable to highly conducting liquids), where T e is the electric relaxation time of charges, and T b is the breakup time in a Lagrangian framework following the liquid jet at its average axial velocity. The influence of the electrical Bond’s number and viscosity on (i) the capillary Rayleigh’s most probable breakup length, (ii) the breakup time, (iii) the volume of the satellite, and (iv) the charge of both main drop and satellite, are analyzed. The model is related to the microjet break-up phenomena in the electrospraying of liquids in steady cone-jet mode, and its range of applicability to those particular problems discussed. Previous experimental results [Mutoh et al., 1979, Convergence and disintegration of liquid jets induced by an electrostatic field. J. Appl. Phys. 50, 3174–3179; Clopeau and Prunet-Foch, 1989, Electrostatic spraying of liquids in cone-jet mode. J. Electrostatics 22, 135–159.] support our numerical finding that the influence of the electrical Bond’s number on Rayleigh’s length is small within the usual parametrical limits of stability of a steady Taylor cone-jet at atmospheric pressure.

Spray Characteristics of Liquid Jet Traversing Subsonic Airstreams

The spray characteristics of a liquid jet traversing subsonic airstreams were experimentally investigated. The disintegration phenomena of liquid jets were observed by instantaneous photographs and high-speed video movies. The waves on the liquid jet surface are three dimensional and show very complicated behaviors. These waves are an important cause of the liquid jet disintegration. Droplet mass e uxes were measured using an isokinetic sampling probe. Empirical equations of their distributions that are expressed by the standard normal function were deduced. Droplet sizes and droplet velocities were measured by a phase Doppler particle analyzer. At low air velocity, the mean droplet diameter reaches its maximum in the peripheral mixing region. At high air velocity, however, the mean droplet diameter reaches its maximum in the core region. The droplet velocity peaks in the peripheral mixing region over the whole range of the air velocity.

Mass Flux Distribution of Spray Formed by Liquid Jet Disintegration in Subsonic Air Streams.

The mass flux distribution of spray formed by liquid jet disintegration in subsonic air streams was measured experimentally, and the empirical equation of the mass flux distribution was deduced. The configuration of the upper profile of the spray mass flux in the liquid injection direction above the peak of the profile is different with that of the lower profile. With increasing the momentum ratio of the liquid and the air, the location in the liquid injection direction where the mass flux becomes maximum is elevated, and the maximum mass flux decreases. With increasing momentum ratio, the number of spray droplets formed at the liquid jet surface before the liquid jet breakup point increases, and contour lines of the spray mass flux show a kidney-shaped configuration near the liquid jet breakup point. Downstream of the liquid jet breakup point the maximum mass flux decreases, and the mass flux profile becomes flatter.

Liquid Jet Disintegration and Spray Characteristics in Subsonic Air Streams.

The present study focuses on the problem of a liquid jet injected transversely into a subsonic air stream. Droplet sizes and droplet velocities were measured, and empirical equations of mean droplet size and mean droplet velocity profile were deduced. On the basis of the observation, the spray formation mechanism is classified into two mechanisms : one due to the instability of the liquid jet surface and the other due to the instability of the liquid jet itself. The maximum size of the mean droplet size profile in the liquid injection direction decreases with increasing air velocity and decreasing momentum ratio of the liquid and the air. The location in the liquid injection direction where the mean droplet velocity becomes minimum is coincident with the location where the mean droplet size becomes maximum. There is a strong correlation between the droplet size and droplet velocity, and larger particles have smaller velocities.

Disintegration of liquid and slurry jets traversing subsonic airstreams

Disintegration of liquid and slurry jets traversing subsonic airstreams

On the Occurence of Droplet Oscillations During Liquid Jet Disintegration.

On the Occurence of Droplet Oscillations During Liquid Jet Disintegration.