Numerical study of the primary breakup of a plane liquid sheet with co-flowing air streams

PAMM ◽  
2012 ◽  
Vol 12 (1) ◽  
pp. 513-514
Author(s):  
Suresh kumar Kannan ◽  
Bernhard Peters
Keyword(s):  
Numerical Study ◽  
Liquid Sheet ◽  
Primary Breakup ◽  
Air Streams

Numerical Study of Non-Newtonian Liquid Sheet Primary Breakup

2011 ◽  
Vol 130-134 ◽  
pp. 3628-3631
Author(s):  
L.P. He ◽  
Z.Y. Xia
Keyword(s):  
Free Surface ◽  
Stokes Equations ◽  
Numerical Study ◽  
Piecewise Linear ◽  
Surface Force ◽  
Liquid Sheet ◽  
Newtonian Liquid ◽  
Navier Stokes ◽  
Primary Breakup ◽  
Atomization Characteristics

Dynamic atomization processes of non-Newtonian liquid were investigated by the method of numerical simulation. The full transient process of the primary instability, deformation, and fragmentation of free surface were simulated numerically by solving the Navier-Stokes equations using an algorithm based on the finite volume method. The tracking of the free surface was achieved using the volume of fluid (VOF) technique and the geometric reconstruction was based on the technique of Piecewise-Linear Interface Construction (PLIC). The continuum surface force (CSF) method was used to model surface tension. In this paper, atomization characteristics of non-Newtonian liquid were analyzed detailedly. The distribution of dimensionless potential length against time was obtained, and the dimensionless wavelength of primary waves was investigated.

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.

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.

scholarly journals Longitudinal instabilities in an air-blasted liquid sheet

2001 ◽  
Vol 437 ◽  
pp. 143-173 ◽  
Author(s):  
ANTONIO LOZANO ◽  
FÉLIX BARRERAS ◽  
GUILLERMO HAUKE ◽  
CÉSAR DOPAZO
Keyword(s):  
Boundary Layer ◽  
Oscillation Frequency ◽  
Numerical Study ◽  
Near Field ◽  
Interface Velocity ◽  
Liquid Sheet ◽  
Linear Instability ◽  
Air Velocity ◽  
Instability Analysis ◽  
Sheet Breakup

An experimental and numerical study has been performed to improve the understanding of the air/liquid interaction in an air-blasted breaking water sheet. This research is focused in the near field close to the exit slit, because it is in this region where instabilities develop and grow, leading to the sheet breakup. In the experiments, several relevant parameters were measured including the sheet oscillation frequency and wavelength, as well as the droplet size distribution and the amplification growth rate. The flow was also investigated using linear instability theory. In the context of existing papers on instability analysis, the numerical part of this work presents two unique features. First, the air boundary layer is taken into account, and the effects of air and liquid viscosity are revealed. Second, the equations are solved for the same parameter values as those in the experiments, enabling a direct comparison between calculations and measurements; although qualitatively the behaviour of the measured variables is properly described, quantitative agreement is not satisfactory. Limitations of the instability analysis in describing this problem are discussed. From all the collected data, it is confirmed that the oscillation frequency strongly depends on the air speed due to the near-nozzle air/water interaction. The wave propagates with accelerating interface velocity which in our study ranges between the velocity of the water and twice that value, depending on the air velocity. For a fixed water velocity, the oscillation frequency varies linearly with the air velocity. This behaviour can only be explained if the air boundary layer is considered.

Linear Instability Analysis of an Annular Liquid Sheet With Inner and Outer Gas Flow

2009 ◽  
Author(s):  
Fathollah Ommi ◽  
Seid Askari Mahdavi ◽  
S. Mostafa Hosseinalipour ◽  
Ehsan Movahednejad
Keyword(s):  
Growth Rate ◽  
Dispersion Equation ◽  
Liquid Sheet ◽  
Linear Instability ◽  
Wave Number ◽  
Unstable Wave ◽  
Instability Analysis ◽  
Air Stream ◽  
Linear Instability Analysis ◽  
Air Streams

A linear instability analysis of an inviscid annular liquid sheet emanating from an atomizer subjected to inner and outer swirling air streams has been carried out. The dimensionless dispersion equation that governs the instability is derived. The dispersion equation solved by Numerical method to investigate the effects of the liquid-gas swirl orientation on the maximum growth rate and its corresponding unstable wave number that it produces the finest droplets. To understand the effect of air swirl orientation with respect to liquid swirl direction, four possible combinations with both swirling air streams with respect to the liquid swirl direction have been considered. Results show that at low liquid swirl Weber number a combination of co-inner air stream and counter-outer air stream has the largest most unstable wave number and shortest breakup length. The combination of inner and the outer air stream co-rotating with the liquid has the highest growth rate.

Numerical Investigation of the Unstable Wave on a Planar Liquid Sheet Produced by an Air-Blast Atomizer

2014 ◽  
Author(s):  
Hua Zhou ◽  
Chia-fon F. Lee ◽  
Timothy H. Lee
Keyword(s):  
Relative Motion ◽  
Internal Flow ◽  
Particle Method ◽  
Liquid Sheet ◽  
Shear Instability ◽  
Unstable Wave ◽  
Air Blast ◽  
Primary Breakup ◽  
Specific Frequency ◽  
Fluid Particles

The unstable surface wave on a liquid sheet produced by an air-blast atomizer during primary breakup process was investigated by numerical simulation. The results of simulation were verified by comparison of primary breakup time and breakup length with accessible experimental data reported in technical papers. The frequency characteristics of stream-wise unstable wave at different axial locations were investigated by applying Discrete Fourier Transform (DFT). It was found that when there is no disturbance induced by internal flow, there is no specific frequency which is favored by shear instability near the nozzle exit, and the characteristic frequency of the dominant wave decreases along stream-wise direction due to the decrease of relative velocity. By applying Discrete Particle Method (DPM), the motion of fluid particles inside the liquid sheet was able to be tracked, and the Lagrangian characteristics of fluid particles can be partially revealed. The growth of stream-wise unstable wave was found to possess strong spatial characteristics by investigating the pathlines and streaklines of fluid particles. A rough evaluation for the stream-wise speed of fluid particles and the propagation velocity of unstable wave showed that fluid particles move faster than unstable wave in stream-wise direction, thus, relative motion exists between fluid particles and stream-wise wave. This relative motion could lead to huge acceleration of fluid particles, which could trigger Rayleigh-Taylor (RT) instability to induce transverse disintegration. Some complex behaviors of fluid particles inside the liquid sheet were observed, e.g. eddy-like structures formed by fluid particles.

LIQUID SHEET DISINTEGRATION BY IMPINGING AIR STREAMS

1991 ◽  
Vol 1 (2) ◽  
pp. 155-170 ◽  
Author(s):  
J. E. Beck ◽  
Arthur H. Lefebvre ◽  
T. R. Koblish
Keyword(s):  
Liquid Sheet ◽  
Air Streams
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