Properties of Nonturbulent Round Liquid Jets in Uniform Crossflows

Aalburg, Christian; Sallam, Khaled; Faeth, G. M.

doi:10.2514/6.2004-969

Cited by 21 publications

(31 citation statements)

References 44 publications

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“…The droplet is assumed to be initially motionless and it is subjected to a step change of the gas phase velocity leading to We numbers in the range 15-90. The ambient air has a high temperature in the range 600-1000K (Tcr,C10=617.7K) which correspond to high density and viscosity ratios (ε>1200 and N>20 respectively) and thus the breakup outcome is not affected by them since ε>32 [24]. The aforementioned combination of We numbers and gas phase temperatures corresponds to gas phase velocities in the range 77-243m/s; these in turn correspond to Re numbers in the range 84-367 which ensures that the flow remains laminar and axisymmetric [69,70]; the Mach numbers are below 0.38, which implies that the compressibility effects can be ignored.…”

Section: Cases Examined and Numerical Setupmentioning

confidence: 99%

“…Selective experimental studies on droplet breakup are those of [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] but generally, there is a scattering of the experimental findings which is probably due to the variety of the experimental techniques used and the experimental uncertainties. Numerical works aiming to fill the gap in knowledge such as those of [23][24][25][26][27][28][29][30][31][32]; they have examined the isothermal droplet breakup in 2-D and 3-D computational domains and they have provided useful information into the detailed processes inside and in the vicinity of the droplets during droplet breakup, which are difficult to be determined with experimental techniques. More specifically, [7][8][9][10] provided breakup maps in the We-Oh plane, [11][12][13]16] further clarified the boundaries between different breakup regimes, [14,15,20,23,25,30,31] clarified the physical mechanisms behind the breakup regimes, [13,18] examined the size distribution of ...…”

Section: Introductionmentioning

confidence: 99%

“…Numerical works aiming to fill the gap in knowledge such as those of [23][24][25][26][27][28][29][30][31][32]; they have examined the isothermal droplet breakup in 2-D and 3-D computational domains and they have provided useful information into the detailed processes inside and in the vicinity of the droplets during droplet breakup, which are difficult to be determined with experimental techniques. More specifically, [7][8][9][10] provided breakup maps in the We-Oh plane, [11][12][13]16] further clarified the boundaries between different breakup regimes, [14,15,20,23,25,30,31] clarified the physical mechanisms behind the breakup regimes, [13,18] examined the size distribution of the child droplets after the parent droplet disintegration, [22] identified experimentally the gas flow structure during droplet breakup, [15,24,26,32] examined the effect of density ratio and [26,27,29,31] examined the droplet drag coefficient. For a detailed presentation of the works referring to droplet breakup, see Strotos et al [33].…”

Section: Introductionmentioning

confidence: 99%

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Aerodynamic breakup of an n -decane droplet in a high temperature gas environment

Strotos

Malgarinos

Νikolopoulos

et al. 2016

Fuel

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The aerodynamic droplet breakup under the influence of heating and evaporation is studied numerically by solving the Navier-Stokes, energy and transport of species conservation equations; the VOF methodology is utilized in order to capture the liquid-air interphase. The conditions examined refer to an n-decane droplet with Weber numbers in the range 15-90 and gas phase temperatures in the range 600-1000K at atmospheric pressure. To assess the effect of heating, the same cases are also examined under isothermal conditions and assuming constant physical properties of the liquid and surrounding air. Under non-isothermal conditions, the surface tension coefficient decreases due to the droplet heat-up and promotes breakup. This is more evident for the cases of lower Weber number and higher gas phase 2 temperature. The present results are also compared against previously published ones for a more volatile n-heptane droplet and reveal that fuels with a lower volatility are more prone to breakup. A 0-D model accounting for the temporal variation of the heat/mass transfer numbers is proposed, able to predict with sufficient accuracy the thermal behavior of the deformed droplet.

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Section: Cases Examined and Numerical Setupmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Aerodynamic breakup of an n -decane droplet in a high temperature gas environment

Strotos

Malgarinos

Νikolopoulos

et al. 2016

Fuel

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“…They found that by increasing the Re number the critical We number, that separates the different breakup regimes, decreases. The work of [10] used the Level-Set method in a 2-D axisymmetric domain to investigate the deformation of droplets at small Re numbers and density ratios (2-32); they found that for density ratios above 32 the boundaries of the breakup regimes are almost unaffected by the density ratio. Furthermore, [11] simulated impulsively accelerated drops using a moving mesh interface tracking scheme and found that the drag coefficient is not affected much by the density ratio although it is larger than those of solid spheres at the same Re numbers.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of the aerodynamic breakup of diesel droplets under various gas pressures

Stefanitsis

Malgarinos

Strotos

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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The present study investigates numerically the aerodynamic breakup of Diesel droplets for a wide range of ambient pressures encountered in engineering applications relevant to oil burners and internal combustion engines. The numerical model solves the Navier-Stokes equations coupled with the Volume of Fluid (VOF) methodology utilized for capturing the interface between the liquid and the surrounding gas. An adaptive local grid refinement technique is used to increase the accuracy of the numerical results around the interface. The Weber (We) numbers examined are in the range of 14 to 279 which correspond to bag, multimode and sheet-thinning breakup regimes. Model results are initially compared against published experimental data and show a good agreement in predicting the drop deformation and the different breakup modes. The predicted breakup initiation times for all cases lie within the theoretical limits given by empirical correlations based on the We number. Following the model validation, the effect of density ratio on the breakup process is examined by varying the gas density (or equivalently the ambient pressure), while the We number is kept almost constant equal to 270; ambient gas pressure varies from 1 up to 146bar and the corresponding density ratios (ε) range from 700 down to 5. Results indicate that the predicted breakup mode of sheet-thinning remains unchanged for changing the density ratio. Useful information about the instantaneous drag coefficient (Cd) and surface area as functions of the selected non-dimensional time is given. It is shown that the density ratio is affecting the drag coefficient, in agreement with previous numerical studies. KeywordsDroplet breakup, Diesel, VOF, density ratio, breakup initiation time. IntroductionDroplet motion, deformation and breakup are observed in a wide variety of engineering applications such as in the injection systems of oil burners and internal combustion engines. Droplet deformation and subsequent breakup are caused by aerodynamic forces exerted on the drop by the surrounding gas, while surface tension and viscosity of the drop hinder deformation and tend to restore it to a spherical shape. The non-dimensional numbers that account for these effects are the Weber (We), Ohnesorge (Oh) and Reynolds (Re) numbers as well as the density (ε) and viscosity (N) ratios of the two phases [1]; the timescale used to non-dimensionalise the time is the shear breakup timescale [2]. For low Oh numbers (Oh<0.1) the droplet breakup is mainly controlled by the We number and according to [1] four different breakup regimes are observed as the We number increases. For We numbers in the range of 11 up to 35 the bag breakup mode is encountered during which the drop deforms into a bag resembling shape. As the We number is further increased up to 80, the multimode regime starts to appear which is essentially a combination of the bag and sheet-thinning modes. In the sheet-thinning breakup mode (80

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“…Level set based numerical methods are popular for simulations of multiphase or multimaterial incompressible flows with complex topological changes [5,6,7,8,9] . The approach has also been used in simulating flows in the microscale by using an adaptive level set method [10] which can achieve the higher resolution required for microfluidic multiphase studies with minimum additional cost.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulations of Two-Phase Flows in Micro Gas/Liquid Mixing Sections

Tatineni

Zhong

2005

43rd AIAA Aerospace Sciences Meeting and Exhibit

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This paper presents a numerical study of multiphase flows in a micro gas/liquid mixing section. The numerical simulation tool is based on the level set advection equation coupled with incompressible Navier-Stokes equations in both the gas and liquid phases. The numerical scheme is based on a standard staggered Marker and Cell (MAC) grid for discretization. The spatial discretization is carried out by using a fifth order Weighted Essentially Non-Oscillatory (WENO) scheme for the convective terms and a second order discretization for all other terms. The numerical simulation tool is used to study a cross-shaped gas/liquid mixing section which produces monodisperse gas bubbles coflowing with liquids in a micro-channel. The surface tension, liquid flow rates and gas flow rates are varied to study the bubble generation process. A simple theoretical model is also developed to predict the size of the bubbles generated. The numerical results are in good agreement with both the theoretical and experimental results. Further simulations are carried out with a T-shaped mixing section to validate the proposed theoretical model. All numerical simulations are also checked and found to be grid independent.

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Properties of Nonturbulent Round Liquid Jets in Uniform Crossflows

Cited by 21 publications

References 44 publications

Aerodynamic breakup of an n -decane droplet in a high temperature gas environment

Aerodynamic breakup of an n -decane droplet in a high temperature gas environment

Numerical investigation of the aerodynamic breakup of diesel droplets under various gas pressures

Numerical Simulations of Two-Phase Flows in Micro Gas/Liquid Mixing Sections

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