A Functional Correlation for the Primary Breakup Processes of Liquid Sheets Emerging From Air-Assist Atomizers

2006 ◽  
Vol 129 (2) ◽  
pp. 188-193 ◽  
Author(s):  
V. Sivadas ◽  
M. V. Heitor ◽  
Rui Fernandes
Keyword(s):  
High Speed ◽  
Imaging Techniques ◽  
Flux Ratio ◽  
Liquid Sheet ◽  
Spray Angle ◽  
High Speed Imaging ◽  
Liquid Sheets ◽  
Primary Breakup ◽  
Sheet Breakup ◽  
The Stability

The study aims to highlight a general relationship between the characteristic variables of liquid sheet breakup and the principal forces of the flow domain. To accomplish this objective, an experimental investigation on air-assisted liquid sheets was carried out for a range of liquid-to-air velocities. The associated spray angle, breakup frequency, and breakup length were measured by exploiting high-speed imaging techniques. The results demonstrate that, when the stability variables are related to the liquid–air momentum flux ratio, a high correlation was attained for a range of flow conditions where capillary instability is insignificant.

High Speed Imaging Techniques For Pulse Nuclear Radiation Source

1989 ◽  
Author(s):  
Wang Kuilu ◽  
Lu Ming ◽  
Liu Cunfu ◽  
Kang Dechun
Keyword(s):  
Radiation Source ◽  
High Speed ◽  
Imaging Techniques ◽  
Nuclear Radiation ◽  
High Speed Imaging

scholarly journals Progress in the Smoothed Particle Hydrodynamics Method to Simulate and Post-process Numerical Simulations of Annular Airblast Atomizers

2020 ◽  
Vol 105 (4) ◽  
pp. 1119-1147
Author(s):  
G. Chaussonnet ◽  
T. Dauch ◽  
M. Keller ◽  
M. Okraschevski ◽  
C. Ates ◽  
...  
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Flux Ratio ◽  
Liquid Sheet ◽  
Sph Method ◽  
Post Process ◽  
Finite Time Lyapunov Exponent ◽  
Fragmentation Spectrum ◽  
Particle Hydrodynamics ◽  
Primary Breakup ◽  
Smoothed Particle

AbstractThis paper illustrates recent progresses in the development of the smoothed particle hydrodynamics (SPH) method to simulate and post-process liquid spray generation. The simulation of a generic annular airblast atomizer is presented, in which a liquid sheet is fragmented by two concentric counter swirling air streams. The accent is put on how the SPH method can bridge the gap between the CAD geometry of a nozzle and its characterization, in terms of spray characteristics and dynamics. In addition, the Lagrangian nature of the SPH method allows to extract additional data to give further insight in the spraying process. First, the sequential breakup events can be tracked from one large liquid blob to very fine stable droplets. This is herein called the tree of fragmentation. From this tree of fragmentation, abstract quantities can be drawn such as the breakup activity and the fragmentation spectrum. Second, the Lagrangian coherent structures in the turbulent flow can be determined easily with the finite-time Lyapunov exponent (FTLE). The extraction of the FTLE is particularly feasible in the SPH framework. Finally, it is pointed out that there is no universal and ultimate non-dimensional number that can characterize airblast primary breakup. Depending on the field of interest, a non-dimensional number (e.g. Weber number) might be more appropriate than another one (e.g. momentum flux ratio) to characterize the regime, and vice versa.

Experimental study of fibre breakup and shot formation in melt blowing nozzle designs

2020 ◽  
pp. 152808372094927 ◽  
Author(s):  
Ignacio Formoso ◽  
Alejandro Rivas ◽  
Gerardo Beltrame ◽  
Gorka S Larraona ◽  
Juan Carlos Ramos ◽  
...  
Keyword(s):  
Experimental Study ◽  
High Speed ◽  
Flux Ratio ◽  
Adhesive Bond ◽  
Operating Conditions ◽  
Nozzle Geometry ◽  
Dimensionless Temperature ◽  
Melt Blowing ◽  
High Speed Imaging ◽  
Adhesive Bonds

The high demand for quality in the manufacture of absorbent hygiene products requires the adhesive bonds between layers to be as uniform as possible. An experimental study was conducted on two industrial multihole melt blowing nozzle designs used for hot-melt adhesive applications for hygiene products, in order to study two defects that influence the quality of the adhesive bond: fibre breakup, resulting in contamination, and the presence of shots, undesirable lumps that end up in the finished product. To this end, the fibre dynamics were captured at the nozzle exit region by using high-speed imaging. From the results it was observed that die drool is the main source of shot formation, while fibre breakup occurs as a result of applying a sufficiently large force in the direction perpendicular to the fibre. In addition, three dimensionless parameters were defined, the first two being the air-polymer flux ratio and the dimensionless temperature ratio, both of which represent the operating conditions, and the remaining one being the force ratio, which represents the nozzle geometry. The effect of these parameters on fibre breakup and shot formation was studied and the results indicate that both the operating conditions and the nozzle geometry were responsible for the onset of the fibre breakup and for the formation of shots. More precisely, both defects turned out to be dominated by the air-polymer flux ratio and the air tilt angle. The results that emerge from this study are useful for the enhancement of industrial melt blowing nozzles.

Atomization of acoustically forced liquid sheets

2019 ◽  
Vol 880 ◽  
pp. 653-683 ◽  
Author(s):  
Sandip Dighe ◽  
Hrishikesh Gadgil
Keyword(s):  
Acoustic Field ◽  
Cutoff Frequency ◽  
Liquid Sheet ◽  
Liquid Jets ◽  
Liquid Sheets ◽  
Aerodynamic Interaction ◽  
Transverse Acoustic ◽  
External Acoustic Field ◽  
Acoustic Forcing ◽  
Sheet Breakup

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.

The Effect of Crosswind Velocity on the Spray Drift of Flat Fan Nozzle

2019 ◽  
Author(s):  
S. Raza ◽  
K. A. Sallam ◽  
S. L. Post
Keyword(s):  
Liquid Sheet ◽  
Nozzle Geometry ◽  
Target Area ◽  
Spray Drift ◽  
Agricultural Industry ◽  
Injection Angle ◽  
Drift Flux ◽  
Breakup Mechanism ◽  
Primary Breakup ◽  
Sheet Breakup

Abstract The objective of this research project is to eliminate the spray drift caused by crosswind. Spray drift is an important problem for the agricultural industry. Some herbicides (e.g. Dicamba) can cause serious damage if it drifts to nearby crops that are not genetically modified to withstand those herbicides. Our hypothesis is that the nozzle geometry and the injection angle can be actively/passively controlled to compensate for the crosswind velocity and effectively deliver the herbicides to the target area. The measurements include the breakup regime transitions, the droplet sizes, and the droplets trajectory as function of the wind speed and the injection angle. The current results show that the crosswind modifies the primary breakup mechanism from sheet breakup regime (i.e. thinning and fragmentation of the liquid sheet into ligaments) to bag breakup regime (i.e. the formation bags along the downstream side of liquid sheet) resulting in smaller drop sizes and an increased drift flux. Techniques to eliminate the bag breakup regime are presented.

Special high speed imaging techniques using phase, aperture, and polarization effects

2013 ◽  
Author(s):  
Wenjing Zhao ◽  
Daniel C. Skaloud ◽  
Sascha Kutz ◽  
Hendrik Rothe ◽  
Cornelius F. Hahlweg
Keyword(s):  
High Speed ◽  
Imaging Techniques ◽  
High Speed Imaging ◽  
Polarization Effects

Liquid Sheet Breakup in Gas-Centered Swirl Coaxial Atomizers

2010 ◽  
Vol 132 (1) ◽  
Author(s):  
V. Kulkarni ◽  
D. Sivakumar ◽  
C. Oommen ◽  
T. J. Tharakan
Keyword(s):  
Flow Behavior ◽  
Liquid Sheet ◽  
Liquid Sheets ◽  
Sheet Surface ◽  
Air Jet ◽  
Entrainment Process ◽  
Sheet Breakup ◽  
Experimental Fluids ◽  
Flow Experiments

The study deals with the breakup behavior of swirling liquid sheets discharging from gas-centered swirl coaxial atomizers with attention focused toward the understanding of the role of central gas jet on the liquid sheet breakup. Cold flow experiments on the liquid sheet breakup were carried out by employing custom fabricated gas-centered swirl coaxial atomizers using water and air as experimental fluids. Photographic techniques were employed to capture the flow behavior of liquid sheets at different flow conditions. Quantitative variation on the breakup length of the liquid sheet and spray width were obtained from the measurements deduced from the images of liquid sheets. The sheet breakup process is significantly influenced by the central air jet. It is observed that low inertia liquid sheets are more vulnerable to the presence of the central air jet and develop shorter breakup lengths at smaller values of the air jet Reynolds number Reg. High inertia liquid sheets ignore the presence of the central air jet at smaller values of Reg and eventually develop shorter breakup lengths at higher values of Reg. The experimental evidences suggest that the central air jet causes corrugations on the liquid sheet surface, which may be promoting the production of thick liquid ligaments from the sheet surface. The level of surface corrugations on the liquid sheet increases with increasing Reg. Qualitative analysis of experimental observations reveals that the entrainment process of air established between the inner surface of the liquid sheet and the central air jet is the primary trigger for the sheet breakup.

Modeling of Gas-Liquid Flow in Pressure Swirl Atomizers

2005 ◽  
Author(s):  
Ashraf A. Ibrahim ◽  
Milind A. Jog
Keyword(s):  
Liquid Flow ◽  
Industrial Applications ◽  
Liquid Sheet ◽  
Spray Angle ◽  
Nozzle Geometry ◽  
Two Phase ◽  
Non Linear ◽  
Sheet Breakup ◽  
Gas Liquid Flow ◽  
Pressure Swirl

Pressure swirl or simplex atomizers are commonly used in a number of industrial applications for liquid atomization, including fuel injection systems for gas turbine engines, spray drying, and paint sprays. Computational modeling of the two-phase flow in the atomizer coupled with a non-linear analysis of instability of liquid sheet exiting from the atomizer has been carried out. The Volume-of-Fluid method is employed to determine the two-phase gas-liquid flow inside the atomizer. Results are validated using available experimental data for film thickness at exit, spray angle, and discharge coefficient. The predictions of breakup length using the non-linear model are compared with available experimental measurements which show excellent agreement. The effect of flow conditions and nozzle geometry on the flow field and sheet breakup are investigated. The coupled internal flow simulation and sheet instability analysis provides a comprehensive approach to modeling atomization from a pressure-swirl atomizer.

High‐speed imaging techniques for harpsichord plucking action.

2010 ◽  
Vol 127 (3) ◽  
pp. 1733-1733
Author(s):  
Marshall J. Brown ◽  
C.‐Y. Jack Perng ◽  
Thomas D. Rossing ◽  
Juliette W. Ioup
Keyword(s):  
High Speed ◽  
Imaging Techniques ◽  
High Speed Imaging
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