Simulation of Laminar Liquid Jets in Gaseous Crossflow Before the Onset of Primary Breakup

2011 ◽  
Author(s):  
C.-L. Ng ◽  
K. A. Sallam
Keyword(s):  
Experimental Data ◽  
Fuel Injection ◽  
Liquid Jets ◽  
Liquid Jet ◽  
Jet Breakup ◽  
Primary Breakup ◽  
Density Ratios ◽  
First Time ◽  
Two Sides ◽  
Reduced Pressures

The deformation of laminar liquid jets in gaseous crossflow before the onset of primary breakup is studied motivated by its application to fuel injection in jet afterburners and agricultural sprays, among others. Three crossflow Weber numbers that represent three different liquid jet breakup regimes; column, bag, and shear breakup regimes, were studied at large liquid/gas density ratios and small Ohnesorge numbers. In each case the liquid jet was simulated from the jet exit and ended before the location where the experimental data indicated the onset of breakup. The results show that in column and bag breakup, the reduced pressures along the sides of the jet cause the liquid to move to the sides of the jet and enhance the jet deformation. In shear breakup, the flattened upwind surface pushes the liquid towards the two sides of the jet and causing the gaseous crossflow to separate near the edges of the liquid jet thus preventing further deformation before the onset of breakup. It was also found out that in shear breakup regime, the liquid phase velocity inside the liquid jet was large enough to cause onset of ligament formation along the jet side, which was not the case in the column and bag breakup regimes. In bag breakup, downwind surface waves were observed to grow along the sides of the liquid jet triggered a complimentary experimental study that confirmed the existence of those waves for the first time.

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

Energies ◽  
2018 ◽  
Vol 11 (7) ◽  
pp. 1854 ◽  
Author(s):  
Jin-Peng Guo ◽  
Yi-Bo Wang ◽  
Fu-Qiang Bai ◽  
Fan Zhang ◽  
Qing Du
Keyword(s):  
Power Law ◽  
Liquid Velocity ◽  
Linear Instability ◽  
Liquid Jets ◽  
Liquid Jet ◽  
Critical Curves ◽  
Jet Breakup ◽  
Plane Jets ◽  
Gas Space ◽  
Aerodynamic Asymmetry

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.

scholarly journals Simulation of Elliptical Liquid Jet Primary Breakup In Supersonic Crossflow

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Yao-zhi Zhou ◽  
Feng Xiao ◽  
Qing-lian Li ◽  
Chen-yang Li
Keyword(s):  
Aspect Ratio ◽  
Penetration Depth ◽  
Horseshoe Vortex ◽  
Liquid Jets ◽  
Liquid Jet ◽  
Breakup Length ◽  
Aspect Ratios ◽  
Primary Breakup ◽  
Elliptical Jet ◽  
Maximum Spreading

The study of elliptical liquid jets in supersonic flow in a Mach 2.0 is performed numerically. The primary breakup process of the elliptical liquid jet is simulated for a Weber number 223, liquid/gas flux momentum 4.0. The aspect ratios of elliptical geometries are set to be 0.25, 0.5, 1, 2, and 5. The results show a remarkable difference in liquid jet disintegration morphology at different aspect ratios. Under supersonic crossflow conditions, the elliptical liquid jet shows more breakup characteristics than the round liquid jet. As the aspect ratio grows, the penetration depth decreases. The elliptical liquid jet with AR=0.25 has the largest penetration depth in all cases. Moreover, the round jet has a maximum spreading angle of 50.2°. The changing trends of the column breakup length both x direction and y direction are similar. The elliptical jet at a lower aspect ratio has a shorter breakup length due to the narrower windward area. The liquid jet has a pair of larger horseshoe vortex structure and a wider wake region at a higher aspect ratio. Two pairs of reversal vortex pairs with obvious characteristics can be observed in all the simulations.

The Breakup Length of Turbulent Liquid Jets

1977 ◽  
Vol 99 (2) ◽  
pp. 414-415 ◽  
Author(s):  
P. Lafrance
Keyword(s):  
Experimental Data ◽  
Statistical Distribution ◽  
Liquid Jets ◽  
Liquid Jet ◽  
Capillary Instability ◽  
Turbulent Fluctuations ◽  
Breakup Length ◽  
Comparison With Experimental Data

A formula for the statistical distribution of the breakup length of a turbulent liquid jet is derived. The formula is based on a model in which random turbulent fluctuations are amplified by capillary instability. A comparison with experimental data is made.

Liquid jet primary breakup in a turbulent cross-airflow at low Weber number

2019 ◽  
Vol 879 ◽  
pp. 775-792 ◽  
Author(s):  
M. Broumand ◽  
M. Birouk ◽  
S. Vahid Mahmoodi J.
Keyword(s):  
Power Law ◽  
Turbulence Intensity ◽  
Weber Number ◽  
Travelling Waves ◽  
Perforated Plate ◽  
Liquid Jet ◽  
Mean Velocity ◽  
Jet Breakup ◽  
Jet Trajectory ◽  
Primary Breakup

The influence of turbulence characteristics of a cross-airflow including its velocity fluctuations and integral length and time scales on the primary breakup regime, trajectory and breakup height and time of a transversely injected liquid jet was investigated experimentally. Turbulence intensity of the incoming airflow was varied from $u_{rms}/u_{g}=1.5\,\%$ to 5.5 % (where $u_{g}$ is cross-airflow streamwise mean velocity and $u_{rms}$ is the r.m.s. of the corresponding cross-airflow streamwise mean velocity fluctuation) by placing at the inlet of the test section a perforated plate/grid with a solidity ratio of $S=50\,\%$. Over the range of gas Weber number, $3.1<We_{g}<7.14$, the ensuing liquid jet exhibited more fluctuations and late breakup transitional behaviour under turbulent airflow conditions than in a uniform cross-airflow. Proper orthogonal decomposition of the liquid jet dynamics revealed that the use of grid caused a rise in the wavelength of travelling waves along the liquid jet, which hindered the transition of the liquid jet primary breakup regime from enhanced capillary breakup to the bag breakup mode. The quantitative results demonstrated that, at a constant airflow mean velocity, turbulent cross-airflow caused the liquid jet to bend earlier compared with its uniform counterpart. A power-law empirical correlation was proposed for the prediction of the liquid jet trajectory which takes into account the effect of turbulent Reynolds number. The liquid jet breakup height (in the $y$-axis direction) normalized by the jet diameter, and accordingly the liquid jet breakup time normalized by the airflow integral time scale, were found to decrease with increasing the airflow turbulence intensity. Two power-law empirical correlations were proposed to predict the liquid jet breakup height and time.

Influence of Nozzle Design Upon the Primary Jet Breakup of High-Viscosity Fuels for Entrained Flow Gasification

2017 ◽  
Author(s):  
Thomas Müller ◽  
Alexa Dullenkopf ◽  
Peter Habisreuther ◽  
Nikolaos Zarzalis ◽  
Alexander Sänger ◽  
...  
Keyword(s):  
Research Work ◽  
Flux Ratio ◽  
Liquid Structure ◽  
High Viscosity ◽  
Design Parameters ◽  
Liquid Jets ◽  
Jet Breakup ◽  
Internal Mixing ◽  
Primary Breakup ◽  
Entrained Flow Gasification

The research work of the present study is focused on the influence of design parameters of twin-fluid nozzles used for the atomization of high-viscosity fuels with respect to the primary breakup of the liquid jet. Two external mixing twin-fluid nozzles, which have already been investigated in previous studies [1, 2], were chosen as basic design. Based on the previous findings the web thickness between fuel and oxidizer supply was varied. In addition both designs were extended by a channel for internal mixing of gas and liquid with a length to diameter ratio of one. Moreover one of the basic nozzles was scaled by decrease of the effective areas in a way that momentum flux ratio as well as gas to liquid mass flow ratio was kept constant. The newly designed atomizers were subsequently investigated with regard to the influence of the changes upon the primary jet breakup using CFD simulations. The numerical simulations were conducted by means of the open source package OpenFOAM. The Volume of Fluid method was used for the determination of the gas-liquid interface. These simulations were then compared with experimentally validated simulations of the basic nozzle designs with regard to the breakup morphology of the jet and the mode of the primary surface instability. In addition, the liquid structure was examined by comparison of breakup length and frequency. The results of these simulations showed that small changes in the atomizer design heavily influence the primary breakup, which in turn influences the overall performance of the atomizer (e.g. SMD). Moreover, these findings will contribute to a better understanding of the physics of the breakup of high-viscosity liquid jets and as well to create an experimentally validated CFD based tool for future burner development and optimization.

CFD Modeling of the Atomization of Plain Liquid Jets in Cross Flow for Gas Turbine Applications

2004 ◽  
Author(s):  
Sachin Khosla ◽  
D. Scott Crocker
Keyword(s):  
Momentum Flux ◽  
Drop Size ◽  
Fuel Injection ◽  
Cross Flow ◽  
Flux Ratio ◽  
Wake Flow ◽  
Cfd Modeling ◽  
Liquid Jets ◽  
Momentum Flux Ratio ◽  
Primary Breakup

A numerical model for liquid jet atomization in a subsonic gas cross flow has been developed and incorporated into a CFD code. The model is designed primarily for the shear breakup regime, which is appropriate for many fuel injection applications. The model considers Weber number and momentum flux ratio ranges that are dominated by either jet surface breakup or column breakup. A boundary layer stripping model has been modified to account for both shearing from the column and shear primary breakup of large drops. Further secondary breakup was modeled with the Rayleigh-Taylor model. The effect of drop distortion on the drag is also considered. Results of the model have been compared with experimental data for jet-A liquid jets in air cross flows with varying pressure, air velocity, and liquid-to-gas momentum flux ratio. Comparisons were made for drop volume flux and drop size as a function of distance from the injector wall. Trends were captured for liquid penetration associated with varying momentum flux ratio, and for drop size as a function distance from the wall. In general, agreement between measurements and CFD predictions were quite good. Areas of disagreement could be reasonably explained by the model’s inherent inability to capture the wake flow behind the liquid column.

Effects of Turbulence on the Breakup of Round Liquid Jets in Gaseous Crossflow

2005 ◽  
Author(s):  
R. Sankarakrishnan ◽  
K. A. Sallam ◽  
F. W. Chambers
Keyword(s):  
Experimental Investigation ◽  
Wind Tunnel ◽  
Test Section ◽  
Drop Size ◽  
Liquid Surface ◽  
Liquid Jets ◽  
Liquid Jet ◽  
Surface Conditions ◽  
Subsonic Wind Tunnel ◽  
Primary Breakup

An experimental investigation of the effects of turbulence on primary breakup of round liquid jets subjected to gaseous crossflow is described. The paper investigates the effects of partial degrees of turbulence development in the liquid. Measurements of the properties of primary breakup were obtained using double-pulsed shadowgraphy in a subsonic wind tunnel having a test section of 0.3 m × 0.3 m × 0.6 m. Measurements included primary breakup regimes, conditions required for the onset of breakup, ligament properties along the liquid surface, drop size and velocity distributions after breakup along the liquid surface, conditions required for breakup of the liquid jet as a whole, and liquid jet trajectories.

Formation and Breakup of Liquid Jets Curved by Gravity

2017 ◽  
Author(s):  
Manash Pratim Borthakur ◽  
Binita Nath ◽  
Gautam Biswas ◽  
Dipankar Bandyopadhyay
Keyword(s):  
Weber Number ◽  
Droplet Size Distribution ◽  
Bond Number ◽  
Liquid Jets ◽  
Liquid Jet ◽  
Horizontal Distance ◽  
Ohnesorge Number ◽  
Jet Breakup ◽  
Jet Trajectory ◽  
Vertical Height

The formation and breakup of a liquid jet in air with gravity acting perpendicular to the direction of the jet is studied computationally. The liquid jet follows a parabolic path due to the influence of gravity which curves the jet trajectory. Both symmetric and asymmetric perturbations develop on the liquid surface which lead to jet breakup with varying droplet size distribution. The limiting length of the jet at breakup increases with increase in the Weber number and Ohnesorge number. At higher value of Weber number, the liquid jet traverses a longer horizontal distance when released from the same vertical height. Increasing the Bond number leads to a significant increase in the curvature of the jet trajectory. The volume of drops produced varies temporally for a given Weber number and decreases with the increasing value of Weber number. The detached drops undergo rolling motion as well as shape oscillations as they continue to fall on their trajectories.

DETECTION OF AERODYNAMIC EFFECTS IN LIQUID JET BREAKUP AND DROPLET FORMATION

1999 ◽  
Vol 9 (4) ◽  
pp. 331-342 ◽  
Author(s):  
Michael P. Moses ◽  
Steven H. Collicott ◽  
Stephen D. Heister
Keyword(s):  
Droplet Formation ◽  
Liquid Jet ◽  
Jet Breakup

PRIMARY BREAKUP OF ROUND AERATED-LIQUID JETS IN SUPERSONIC CROSSFLOWS

2006 ◽  
Vol 16 (6) ◽  
pp. 657-672 ◽  
Author(s):  
K. A. Sallam ◽  
C. Aalburg ◽  
G. M. Faeth ◽  
K.-C. Lin ◽  
C. D. Carter ◽  
...  
Keyword(s):  
Liquid Jets ◽  
Primary Breakup
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