DNS Investigation of the Primary Breakup in a Conical Swirled Jet

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.

Download Full-text

Primary Breakup of Round Nonturbulent Liquid Jets in Gaseous Crossflows

41st Aerospace Sciences Meeting and Exhibit ◽

10.2514/6.2003-1326 ◽

2003 ◽

Cited By ~ 4

Author(s):

Khaled Sallam ◽

Christian Aalburg ◽

Gerard Faeth

Keyword(s):

Liquid Jets ◽

Primary Breakup

Download Full-text

LES of primary breakup of pulsed liquid jet in supersonic crossflow

Acta Astronautica ◽

10.1016/j.actaastro.2018.10.043 ◽

2019 ◽

Vol 154 ◽

pp. 119-132 ◽

Cited By ~ 5

Author(s):

Y.H. Zhu ◽

F. Xiao ◽

Q.L. Li ◽

R. Mo ◽

C. Li ◽

...

Keyword(s):

Liquid Jet ◽

Primary Breakup

Download Full-text

A Validated Two-Phase Flow Large Eddy Simulation Methodology

Volume 3: Gas Turbine Heat Transfer; Transport Phenomena in Materials Processing and Manufacturing; Heat Transfer in Electronic Equipment; Symposium in Honor of Professor Richard Goldstein; Symposium in Honor of Prof. Spalding; Symposium in Honor of Prof. Arthur E. Bergles ◽

10.1115/ht2013-17624 ◽

2013 ◽

Author(s):

Feng Xiao ◽

Mehriar Dianat ◽

James J. McGuirk

Keyword(s):

Boundary Conditions ◽

Level Set ◽

Two Phase Flow ◽

Local Level ◽

Density Ratio ◽

Cross Flow ◽

Liquid Jet ◽

Phase Flow ◽

Two Phase ◽

Primary Breakup

A robust two-phase flow LES methodology is described, validated and applied to simulate primary breakup of a liquid jet injected into an airstream in either co-flow or cross-flow configuration. A Coupled Level Set and Volume of Fluid method is implemented for accurate capture of interface dynamics. Based on the local Level Set value, fluid density and viscosity fields are treated discontinuously across the interface. In order to cope with high density ratio, an extrapolated liquid velocity field is created and used for discretisation in the vicinity of the interface. Simulations of liquid jets discharged into higher speed airstreams with non-turbulent boundary conditions reveals the presence of regular surface waves. In practical configurations, both air and liquid flows are, however, likely to be turbulent. To account for inflowing turbulent eddies on the liquid jet interface primary breakup requires a methodology for creating physically correlated unsteady LES boundary conditions, which match experimental data as far as possible. The Rescaling/Recycling Method is implemented here to generate realistic turbulent inflows. It is found that liquid rather than gaseous eddies determine the initial interface shape, and the downstream turbulent liquid jet disintegrates much more chaotically than the non-turbulent one. When appropriate turbulent inflows are specified, the liquid jet behaviour in both co-flow and cross-flow configurations is correctly predicted by the current LES methodology, demonstrating its robustness and accuracy in dealing with high liquid/gas density ratio two-phase systems.

Download Full-text

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

Flow Turbulence and Combustion ◽

10.1007/s10494-020-00174-6 ◽

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.

Download Full-text

Cusping, capture, and breakup of interacting drops by a curvatureless boundary-integral algorithm

Journal of Fluid Mechanics ◽

10.1017/s0022112099005285 ◽

1999 ◽

Vol 391 ◽

pp. 249-292 ◽

Cited By ~ 64

Author(s):

ALEXANDER Z. ZINCHENKO ◽

MICHAEL A. ROTHER ◽

ROBERT H. DAVIS

Keyword(s):

Three Dimensional ◽

Adaptive Mesh ◽

Boundary Integral ◽

Small Surface ◽

Low Viscosity ◽

Primary Breakup ◽

Dimensional Boundary ◽

Normal Vectors ◽

Passive Technique ◽

Line Singularities

A three-dimensional boundary-integral algorithm for interacting deformable drops in Stokes flow is developed. The algorithm is applicable to very large deformations and extreme cases, including cusped interfaces and drops closely approaching breakup. A new, curvatureless boundary-integral formulation is used, containing only the normal vectors, which are usually much less sensitive than is the curvature to discretization errors. A proper regularization makes the method applicable to small surface separations and arbitrary λ, where λ is the ratio of the viscosities of the drop and medium. The curvatureless form eliminates the difficulty with the concentrated capillary force inherent in two-dimensional cusps and allows simulation of three-dimensional drop/bubble motions with point and line singularities, while the conventional form can only handle point singularities. A combination of the curvatureless form and a special, passive technique for adaptive mesh stabilization allows three-dimensional simulations for high aspect ratio drops closely approaching breakup, using highly stretched triangulations with fixed topology. The code is applied to study relative motion of two bubbles or drops under gravity for moderately high Bond numbers [Bscr ], when cusping and breakup are typical. The deformation-induced capture efficiency of bubbles and low-viscosity drops is calculated and found to be in reasonable agreement with available experiments of Manga & Stone (1993, 1995b). Three-dimensional breakup of the smaller drop due to the interaction with a larger one for λ=O(1) is also considered, and the algorithm is shown to accurately simulate both the primary breakup moment and the volume partition by extrapolation for moderately supercritical conditions. Calculations of the breakup efficiency suggest that breakup due to interactions is significant in a sedimenting emulsion with narrow size distribution at λ=O(1) and [Bscr ][ges ]5–10. A combined capture and breakup phenomenon, when the smaller drop starts breaking without being released from the dimple formed on the larger one, is also observed in the simulations. A general classification of possible modes of two-drop interactions for λ=O(1) is made.

Download Full-text

Understanding High-pressure Injection Primary Breakup by Using Large Eddy Simulation and X-ray Spray Imaging

MTZ worldwide ◽

10.1007/s38313-017-0039-4 ◽

2017 ◽

Vol 78 (5) ◽

pp. 50-57 ◽

Cited By ~ 2

Author(s):

Junmei Shi ◽

Pablo Lopez Aguado ◽

Noureddine Guerrassi ◽

Gavin Dober

Keyword(s):

High Pressure ◽

Large Eddy Simulation ◽

X Ray ◽

Eddy Simulation ◽

Pressure Injection ◽

Large Eddy ◽

Primary Breakup ◽

High Pressure Injection

Download Full-text

Numerical Analysis of the Primary Breakup Under High-Altitude Relight Conditions Applying the Embedded DNS Approach to a Generic Prefilming Airblast Atomizer

Volume 1A: Combustion, Fuels and Emissions ◽

10.1115/gt2013-94446 ◽

2013 ◽

Cited By ~ 2

Author(s):

Benjamin Sauer ◽

Nikolaos Spyrou ◽

Amsini Sadiki ◽

Johannes Janicka

Keyword(s):

Surface Tension ◽

Boundary Conditions ◽

High Altitude ◽

Ambient Pressure ◽

Planar Geometry ◽

Slight Variation ◽

Strong Impact ◽

Wall Film ◽

Primary Breakup ◽

Liquid Wall

The primary breakup under high-altitude relight conditions is investigated in this study where ambient pressure is as low as 0.4 bar and air, fuel and engine parts are as cold as 265 K. The primary breakup is crucial for the fuel atomization. As of today, the phenomena dictating the primary breakup are not fully understood. Direct Numerical Simulations (DNS) of liquid breakup under realistic conditions and geometries are hardly possible. The embedded DNS (eDNS) approach represents a reliable numerical tool to fill this gap. The concept consists of three steps: a geometry simplification, the generation of realistic boundary conditions for the DNS and the DNS of the breakup region. The realistic annular airblast atomizer geometry is simplified to a Y-shaped channel representing a planar geometry. Inside this domain the eDNS is located. The eDNS domain requires the generation of boundary conditions. A Large Eddy Simulation (LES) of the entire Y-shaped channel and a Reynolds-Averaged Navier-Stokes Simulation (RANS) of the liquid wall film are performed prior to the DNS. All parameters are stored transiently on all virtual DNS planes. These variables are then mapped to the DNS. Thus, high-quality boundary conditions are generated. The Volume-of-Fluid (VOF) method is used to solve for the two-phase flow. The results provide a qualitative insight into the primary breakup under realistic high-altitude relight conditions. Instantaneous snapshots in time illustrate the behavior of the liquid wall film along the prefilmer lip and illustrate the breakup process. It is seen that a slight variation of the surface tension force has a strong impact on the appearance of the primary breakup. Case 1 with the surface tension corresponding to kerosene at 293 K indicates large flow structures that are separated from the liquid sheet. By lowering the surface tension related to kerosene at 363 K, the breakup is dominated by numerous small structures and droplets. This study proves the applicability of the eDNS concept for investigating breakup processes as the transient nature of the phase interface behavior can be captured. At this time, the authors only present a qualitative insight which can be explained by the lack of quantitative data. The approach offers the potential of simulating realistic annular highly-swirled airblast atomizer geometries under realistic conditions.

Download Full-text