Fragmentation Of Liquid Droplets Research Articles

Research on Spontaneous Diffusion and Fragmentation of Liquid Droplets Caused by Marangoni Effect

The Marangoni effect is important to drying silicon wafers, the fields of welding and improving engine liquid fuel efficiency. In this paper, we investigate the Marangoni flow caused by the evaporation of droplets of alcohol solution, which eventually causes the droplet "atomization" phenomenon. The Marangoni convection phenomenon was studied in terms of temperature and droplet concentration, and the changes of droplet diffusion and the degree of droplet "atomization" were investigated after droplets of different volume concentrations of Isopropyl Alcohol (IPA) were added to different solutions.

Criterion of drop fragmentation at a collision with a solid target (numerical simulation and experiment)

This paper is devoted to the study of the deformation and fragmentation of liquid droplets when they collide with masks and filters used for protection against infected droplets. In this paper, the local collision of a drop with a mask or filter is modeled numerically and experimentally by the example of the drop impact on a small obstacle. Studies allow tracing the fragmentation of oral and bronchial fluids and their transformation into the number of tiny droplets that spread infection in the air.

Collisions of Liquid Droplets in a Gaseous Medium under Conditions of Intense Phase Transformations: Review

The article presents the results of theoretical and experimental studies of coalescence, disruption, and fragmentation of liquid droplets in multiphase and multicomponent gas-vapor-droplet media. Highly promising approaches are considered to studying the interaction of liquid droplets in gaseous media with different compositions and parameters. A comparative analysis of promising technologies is carried out for the primary and secondary atomization of liquid droplets using schemes of their collision with each other. The influence of a range of factors and parameters on the collision processes of drops is analyzed, in particular, viscosity, density, surface, and interfacial tension of a liquid, trajectories of droplets in a gaseous medium, droplet velocities and sizes. The processes involved in the interaction of dissimilar droplets with a variable component composition and temperature are described. Fundamental differences are shown in the number and size of droplets formed due to binary collisions and collisions between droplets and particles at different Weber numbers. The conditions are analyzed for the several-fold increase in the number of droplets in the air flow due to their collisions in the disruption mode. A technique is described for generalizing and presenting the research findings on the interaction of drops in the form of theoretical collision regime maps using various approaches.

Influence of density ratio on the secondary atomization of liquid droplets under highly unstable conditions

In this paper, the influence of density ratio on the atomization of liquid droplets under highly unstable conditions is numerically investigated with a coupled volume-of-fluid and level-set method. By employing the adaptive mesh refinement technique, the computational cost is significantly reduced and good agreements with experimental measurements on both the morphology and trajectory of droplets are obtained. Specifically, at We=13, the present model correctly predicts bag breakup, which is consistent with earlier studies. Based on the present model, the effects of density ratio on the deformation and fragmentation of liquid droplets are investigated from the aspects of the time-resolved evolutions of gaseous Weber number, drag coefficient, liquid surface structure, as well as the morphology of liquid droplets, with special attention drawn to gain more in-depth insight into the dynamics of fragmentation under the highly unstable conditions (initial gaseous Weber number Weg,i=225, initial gaseous Reynolds number Reg,i=10062.5). The results indicate that the drag coefficient is determined by the recirculation region and therefore largely affected by the density ratio. A lower density ratio may lead to a higher deformation rate, while a higher density ratio results in more intensive fragmentation. Furthermore, the density ratio has a significant effect on the deformation and fragmentation in the investigated conditions when the density ratio exceeds 32 at a small Ohnesorge number.

Azeotropy of alcohol–water mixtures from the viewpoint of cluster-level structures

We showed that there is a close relation between evaporation properties and cluster-level structures in alcohol–water binary mixtures, on the basis of the mass spectrometric analyses of clusters generated through fragmentation of liquid droplets. The azeotropy for alcohol (ethanol, 1-propanol or 1-butanol)–water mixtures is caused by the change of the evaporation properties attributed to the cluster-level structures in the mixtures. When the hydrogen-bonding network of water molecules is stable at the cluster level in the water-rich mixtures, the alcohol molecules included in the water-rich clusters are evaporated primarily. On the other hand, when the alcohol self-association clusters are formed with an increase of the alcohol concentration in the mixtures, evaporation of the water existing around the alcohol self-association clusters is increased.

Microheterogeneity of ethanol–water binary mixtures observed at the cluster level

The microscopic structures in ethanol–water binary mixtures were examined by analyzing the mass spectra of clusters generated through fragmentation of liquid droplets. From the effects of temperature and mixing ratios on the cluster structures, we have demonstrated that the ethanol–water binary mixtures have microscopic phase separation at the cluster level in wide mixing ratios: 10 vol.% < [EtOH] < 90 vol.%. In this region, ethanol-rich clusters whose molecular composition is independent of the mixing ratio were observed at lower temperatures, and the ethanol-rich clusters interacted with water molecules with increasing temperature. Furthermore, we would like to present the mechanism for the formation of ethanol-rich clusters, induced by the contact with water molecules.

Phase separation of water–alcohol binary mixtures induced by the microheterogeneity

The relationship between liquid-liquid phase separation and microheterogeneity in water-primary alcohol mixtures was examined by analysing the mass spectra of clusters generated through the fragmentation of liquid droplets. By comparing the cluster structures of water-ethanol, -1-propanol, and -1-butanol binary mixtures at various alcohol concentrations, we discovered differences in the molecular clusters that control phase separation. We also studied the role of water in alcohol self-association. Alcohol self-association is promoted in the presence of a small amount of water (ca. 10 approximately 20 wt%), in which the water-water hydrogen-bonding network is weak and does not contribute to alcohol self-association. We have demonstrated that alcohol self-association is also promoted by non-ideal mixing with other alcohols. The self-association of alcohol molecules complements the loss of stabilization energy caused by the relatively weak coexisting interactions. This complementary relationship among intermolecular interactions is an inherent property of solutions, and plays a key role in the phase separation process.

Cluster structures determined by ion–molecular interactions: preferential solvation and acid–base neutralization

The neutralization of CH 3COOH by NaOH in water has been studied by the mass spectrometric analysis of clusters generated via fragmentation of liquid droplets. In water, CH 3COOH molecules form self-association clusters at higher acid concentrations like the molar ratio of CH 3COOH:H 2O=1:10. At these concentrations, the neutralization takes place via interaction between the CH 3COOH clusters and NaOH to afford Na +(CH 3COOH) a(CH 3COONa) b clusters. Furthermore, Na + is preferentially solvated by CH 3COOH in water to form Na +(CH 3COOH) α clusters. In consideration with these cluster structure, the reaction mechanism in solution can be realized more precisely.

Cluster Formation of 1-Butanol–Water Mixture Leading to Phase Separation

Microscopic structures of 1-butanol (1-BuOH)–water mixtures in the presence and absence of salts are studied through the mass spectrometric analysis of clusters generated from the fragmentation of liquid droplets. The analysis of cluster structures provides information on the phase separation of 1-BuOH–water mixtures from the microscopic viewpoint. In a saturated solution of 1-BuOH in water, 1-BuOH exists as hydrated 1-BuOH clusters and self-associated 1-BuOH clusters. With further addition of 1-BuOH, a 1-BuOH rich phase is generated. When the salt (LiCl, NaCl, MgCl2, etc.) coexists in the 1-BuOH–water mixtures, the cation is preferentially solvated by the 1-BuOH to form M +(1-BuOH) m or M 2+(1-BuOH) m clusters: M + = Li+, Na+, Mg2+ = Mg2+, etc., m = 1, 2, 3, ... Since the formation of M +(1-BuOH) m corresponds to an increase of the self-associated 1-BuOH clusters in water, the presence of the salt induces the phase separation at lower 1-BuOH concentrations.

Experimental study concerning the motion and the fragmentation of liquid droplets in a gas stream

This study concerns the motion of single water drops with a diameter from 100 to 300μ in a gradient stream of air with a maximum velocity up to 200 m/sec. Empirical relations are derived for the basic critical numbers characterizing the motion and the acceleration of droplets in an air stream, as functions of time.