Controlling droplet bouncing and coalescence with surfactant

Pan, Kuo-Long; Tseng, Yu-Hau; Chen, Jung-Chieh; Huang, Kuan-Ling; Wang, C. H.; Lai, Ming-Chih

doi:10.1017/jfm.2016.381

Cited by 38 publications

(33 citation statements)

References 60 publications

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“…In this chapter, we will first benchmark our method performing the most commonly used tests, which include also a vis-a-vis comparison against previous experimental results [13,24,28,29,40,47,70,73]. Then we will examine on a qualitative basis the performances of the method on a fully turbulent, surfactant-laden multiphase flow.…”

Section: Resultsmentioning

confidence: 99%

Coalescence of surfactant-laden drops by Phase Field Method

Soligo

Roccon

Soldati

2019

Journal of Computational Physics

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In this work, we propose and test the validity of a modified Phase Field Method (PFM), which was specifically developed for large scale simulations of turbulent flows with large and deformable surfactant-laden droplets. The time evolution of the phase field, φ, and of the surfactant concentration field, ψ, are obtained from two Cahn-Hilliard-like equations together with a two-order-parameter Time-Dependent Ginzburg-Landau (TDGL) free energy functional. The modifications introduced circumvent existing limitations of current approaches based on PFM and improve the well-posedness of the model. The effect of surfactant on surface tension is modeled via an Equation Of State (EOS), further improving the flexibility of the approach. This method can efficiently handle topological changes, i.e. breakup and coalescence, and describe adsorption/desorption of surfactant. The capabilities of the proposed approach are tested in this paper against previous experimental results on the effects of surfactant on the deformation of a single droplet and on the interactions between two droplets. Finally, to appreciate the performances of the model on a large scale complex simulation, a qualitative analysis of the behavior of surfactant-laden droplets in a turbulent channel flow is presented and discussed.

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Section: Resultsmentioning

confidence: 99%

Coalescence of surfactant-laden drops by Phase Field Method

Soligo

Roccon

Soldati

2019

Journal of Computational Physics

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“…By adding surfactants or contaminants, droplet collision modes can be controlled. In particular, mode maps and characteristics of collisions of liquid droplets with surfactants or contaminants are given in [41]. Since, in real technologies, the presence of various impurities in the droplets is possible, and their concentration may change during the process (for example, due to evaporation or burnout), it is further advisable to study the processes of collisions of liquid droplets in an aerosol with the addition of surfactants or contaminants.…”

Section: Experimental Setup and Methodsmentioning

confidence: 99%

Interaction of Liquid Droplets in Gas and Vapor Flows

et al. 2019

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We investigated the conditions, characteristics, and outcomes of liquid droplet interaction in the gas medium using video frame processing. The frequency of different droplet collision outcomes and their characteristics were determined. Four interaction regimes were identified: bounce, separation, coalescence, and disruption. Collision regime maps were drawn up using the Weber, Reynolds, Ohnesorge, Laplace, and capillary numbers, as well as dimensionless linear and angular parameters of interaction. Significant differences were established between interaction maps under ideal conditions (two droplets colliding without a possible impact of the neighboring ones) and collision of droplets as aerosol elements. It was shown that the Weber number could not be the only criterion for changing the collision mode, and sizes and concentration of droplets in aerosols influence collision modes. It was established that collisions of droplets in a gaseous medium could lead to an increase in the liquid surface area by 1.5–5 times. Such a large-scale change in the surface area of the liquid significantly intensifies heat transfer and phase transformations in energy systems.

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“…For binary Newtonian droplet collisions, the current studies [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] are mainly focused on two aspects: from binary low-viscosity droplet collisions to binary high-viscosity droplet collisions, and from binary homogeneous-droplet collisions to binary heterogeneous-droplet collisions. Jiang et al [9] and reflexive separation of droplets were investigated.…”

Section: Introductionmentioning

confidence: 99%

“…Based on the capillary instability and an energy balance, a scaling law for the evolution of the threshold impact velocity was established for head-on collisions. The research of Pan et al [17] identified the key mechanisms governing the impact dynamics of surfactant-coated droplets in the air and imply the potential of using a small amount of surfactant to manipulate impact outcomes. Compared to the Newtonian liquids, relatively few studies [24][25][26][27][28][29][30] have been conducted for the non-Newtonian liquids, which are of relevance to, for example, polymers.…”

mentioning

confidence: 99%

A Numerical Investigation on the Collision Behavior of Polymer Droplets

2020

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Binary droplet collisions are a key mechanism in powder coatings production, as well as in spray combustion, ink-jet printing, and other spray processes. The collision behavior of the droplets using Newtonian and polymer liquids is studied numerically by the coupled level-set and volume of fluid (CLSVOF) method and adaptive mesh refinement (AMR). The deformation process, the internal flow fields, and the energy evolution of the droplets are discussed in detail. For binary polymer droplet collisions, compared with the Newtonian liquid, the maximum deformation is promoted. Due to the increased viscous dissipation, the colliding droplets coalesce more slowly. The stagnant flow region in the velocity field increases and the flow re-direction phenomenon is suppressed, so the polymer droplets coalesce permanently. As the surface tension of the polymer droplets decreases, the kinetic and the dissipated energy increases. The maximum deformation is promoted, and the coalescence speed of the droplets slows down. During the collision process, the dominant pressure inside the polymer droplets varies from positive pressure to negative pressure and then to positive pressure. At low surface tension, due to the non-synchronization in the movement of the interface front, the pressure is not smooth and distributes asymmetrically near the center of the droplets.

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Controlling droplet bouncing and coalescence with surfactant

Cited by 38 publications

References 60 publications

Coalescence of surfactant-laden drops by Phase Field Method

Coalescence of surfactant-laden drops by Phase Field Method

Interaction of Liquid Droplets in Gas and Vapor Flows

A Numerical Investigation on the Collision Behavior of Polymer Droplets

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