Contact Angle Effects on Pore and Corner Arc Menisci in Polygonal Capillary Tubes Studied with the Pseudopotential Multiphase Lattice Boltzmann Model

Son, Soyoun; Chen, Li; Kang, Qinjun; Derome, Dominique; Carmeliet, Jan

doi:10.3390/computation4010012

Cited by 19 publications

(23 citation statements)

References 45 publications

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“…A change in cross-sectional geometry is essentially equivalent to a change in the contact angle between the pore wall and the fluid. This is in-line with more recent results from Son et al (2016), who modelled the menisci formed in triangular and square tubes, equivalent to our three-membered and four-membered ring pores, and reporting the liquid surface to form a hemisphere at equilibrium.…”

Section: Capillary Condensation Within Soot Aggregatessupporting

confidence: 92%

Soot-PCF: Pore condensation and freezing framework for soot aggregates

Marcolli¹,

Mahrt²,

Kärcher³

2020

Preprint

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Abstract. How ice crystals form in the troposphere strongly affects cirrus cloud properties. Atmospheric ice formation is often initiated by aerosol particles that act as ice nucleating particles. The aerosol-cloud interactions of soot and associated feedbacks remain uncertain, in part because a coherent understanding of the ice nucleation mechanism and activity of soot has not yet emerged. Here, we provide a new framework that predicts ice formation on soot particles via pore condensation and freezing (PCF) that, unlike previous approaches, considers soot particle properties capturing their vastly different pore properties compared to other aerosol species such as mineral dust. During PCF, water is taken up below water saturation into pores on soot aggregates by capillary condensation. At cirrus temperatures, pore water can freeze homogeneously and subsequently grow into a macroscopic ice crystal. In the soot-PCF framework presented here, the relative humidity conditions required for these steps are derived for different pore types as a function of temperature. The pore types considered here evolve from idealized stacking of equally sized primary particles, either in tetrahedral or cubic packing arrangements. Specifically, we encompass n-membered ring pores that form between n individual spheres within the same layer of primary particles as well as pores in the form of inner cavities that form between two layers of primary particles. We treat soot primary particles as perfect spheres and use the contact angle between soot and water (θsw), the primary particle diameter (Dpp) and the degree of primary particle overlap (overlap coefficient, Cov) to characterize soot pore properties. We find that n-membered ring pores are the dominant pore structures for soot-PCF, as they are common features of soot aggregates and have a suitable geometry for both, filling with water and growing ice below water saturation. We focus our analysis on three-membered and four-membered ring pores as they are of the right size for PCF assuming primary particle sizes typical for atmospheric soot particles. For these pore types, we derive equations that describe the conditions for all three steps of soot-PCF, namely capillary condensation, ice nucleation, and ice growth. Since at typical cirrus conditions homogeneous ice nucleation can be considered immediate as soon as the water volume within the pore is large enough to host a critical ice embryo, soot-PCF becomes either limited by capillary condensation or ice crystal growth. For instance, our results show that at typical cirrus temperatures of T = 220 K, three-membered ring pores formed between primary particles with θsw = 60°, Dpp = 20 nm, and Cov = 0.05 are ice growth limited, as the ice requires a relative humidity with respect to ice of RHi = 137 % to grow out of the pore, while a sufficient volume of pore water for ice nucleation has condensed already at RHi = 86 %. Conversely, four-membered ring pores with the same primary particle size and an overlap coefficient of Cov = 0.1 are capillary condensation limited as they require RHi = 129 % to gather enough water for ice nucleation, compared with only 124 % RHi, required for ice growth. We use the soot-PCF framework to derive a new equation to parameterize of ice formation on soot particles via PCF. This equation is based on soot properties that are routinely measured, including the primary particle size and overlap, and the fractal dimension. These properties, along with the number of primary particles making up an aggregate and the contact angle between water and soot, constrain the parameterization. Applying the new parameterization to previously reported laboratory data of ice formation on soot particles provides direct evidence that ice nucleation on soot aggregates takes place via PCF. We conclude that this new framework clarifies the ice formation mechanism on soot particles at cirrus conditions and provides a new perspective to represent ice formation on soot in climate models.

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Section: Capillary Condensation Within Soot Aggregatessupporting

confidence: 92%

Soot-PCF: Pore condensation and freezing framework for soot aggregates

Marcolli¹,

Mahrt²,

Kärcher³

2020

Preprint

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“…The primary particles coagulate to form soot clusters that grow further in size into soot aggregates as a result of monomer-cluster or clustercluster collision. Sizes of ambient soot aggregates range from a few primary particles to larger, fractal aggregates with tens to hundreds of primary particles, depending on the combustion source and conditions (Sorensen, 2011;Wentzel et al, 2003). Diameters typically range from 0.01 to 1 µm (Ogren and Charlson, 1983;Rose et al, 2006), but they can also reach larger values depending on the source and atmospheric trajectory (e.g.…”

Section: Soot Propertiesmentioning

confidence: 99%

“…Yet, soot aggregates are not truly fractals because they are not completely scale invariant but exhibit self-similarity only over a finite range of length scales (Huang et al, 1994;Mandelbrot, 1977). Nonetheless, the concepts of fractal geometry have successfully been used to quantitatively describe their morphology during aggregate growth by agglomeration (Sorensen, 2011). To describe soot aggregates as fractals, the primary particles are assumed to all be of the same size with point contacts between each other (Sorensen, 2011).…”

Section: Soot Aggregate Size and Compactionmentioning

confidence: 99%

“…Nonetheless, the concepts of fractal geometry have successfully been used to quantitatively describe their morphology during aggregate growth by agglomeration (Sorensen, 2011). To describe soot aggregates as fractals, the primary particles are assumed to all be of the same size with point contacts between each other (Sorensen, 2011). As a consequence of self-similarity, the number of primary particles scales as a power law with the radius, implying a fractal dimension of 1 for a chain agglomerate and a fractal dimension of 3 for primary particles ordered as a sphere.…”

Section: Soot Aggregate Size and Compactionmentioning

confidence: 99%

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Soot PCF: pore condensation and freezing framework for soot aggregates

2021

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Abstract. Atmospheric ice formation in cirrus clouds is often initiated by aerosol particles that act as ice-nucleating particles. The aerosol–cloud interactions of soot and associated feedbacks remain uncertain, in part because a coherent understanding of the ice nucleation mechanism and activity of soot has not yet emerged. Here, we provide a new framework that predicts ice formation on soot particles via pore condensation and freezing (PCF) that, unlike previous approaches, considers soot particle properties, capturing their vastly different pore properties compared to other aerosol species such as mineral dust. During PCF, water is taken up into pores of the soot aggregates by capillary condensation. At cirrus temperatures, the pore water can freeze homogeneously and subsequently grow into a macroscopic ice crystal. In the soot-PCF framework presented here, the relative humidity conditions required for these steps are derived for different pore types as a function of temperature. The pore types considered here encompass n-membered ring pores that form between n individual spheres within the same layer of primary particles as well as pores in the form of inner cavities that form between two layers of primary particles. We treat soot primary particles as perfect spheres and use the contact angle between soot and water (θsw), the primary particle diameter (Dpp), and the degree of primary particle overlap (overlap coefficient, Cov) to characterize pore properties. We find that three-membered and four-membered ring pores are of the right size for PCF, assuming primary particle sizes typical of atmospheric soot particles. For these pore types, we derive equations that describe the conditions for all three steps of soot PCF, namely capillary condensation, ice nucleation, and ice growth. Since at typical cirrus conditions homogeneous ice nucleation can be considered immediate as soon as the water volume within the pore is large enough to host a critical ice embryo, soot PCF becomes limited by either capillary condensation or ice crystal growth. We use the soot-PCF framework to derive a new equation to parameterize ice formation on soot particles via PCF, based on soot properties that are routinely measured, including the primary particle size, overlap, and the fractal dimension. These properties, along with the number of primary particles making up an aggregate and the contact angle between water and soot, constrain the parameterization. Applying the new parameterization to previously reported laboratory data of ice formation on soot particles provides direct evidence that ice nucleation on soot aggregates takes place via PCF. We conclude that this new framework clarifies the ice formation mechanism on soot particles in cirrus conditions and provides a new perspective to represent ice formation on soot in climate models.

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“…Son et al. (2016) used a pseudopotential multiphase LB model to study the influence of contact angle on arc menisci in polygonal tubes and validated the simulation results with the Mayer and Stoewe‐Princen (MS‐P) theory. Gurumurthy et al.…”

Section: Introductionmentioning

confidence: 99%

Spontaneous Imbibition in a Square Tube With Corner Films: Theoretical Model and Numerical Simulation

Zhao

Qin

Fischer

et al. 2021

Water Resources Research

Self Cite

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Spontaneous imbibition in an angular tube with corner films is a fundamental problem in many scientific and engineering processes. In this study, a modified interacting capillary bundle model is developed to describe the liquid imbibition dynamics in a square tube with corner films. The square tube is decomposed into several interacting subcapillaries and the local capillary pressure in each subcapillary is derived based on the specific shape of its meniscus. The conductance of each subcapillary is calculated using single‐phase lattice Boltzmann simulation. The modified interacting capillary bundle model and color‐gradient lattice Boltzmann method are used to simulate the liquid imbibition dynamics in the square tube with different fluid properties. The predictions by the modified interacting capillary bundle model match well with the lattice Boltzmann simulation results for different conditions, demonstrating the accuracy and robustness of the interacting capillary bundle model to describe the imbibition dynamics with corner films. In addition, the interacting capillary bundle model is helpful to investigate the mechanisms during spontaneous imbibition and the influences of fluid viscosity, surface tension, wetting phase contact angle and gravity on imbibition dynamics. Finally, a universal scaling law of imbibition dynamics for the main meniscus is developed and the scaling law for arc meniscus is also analyzed.

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Contact Angle Effects on Pore and Corner Arc Menisci in Polygonal Capillary Tubes Studied with the Pseudopotential Multiphase Lattice Boltzmann Model

Cited by 19 publications

References 45 publications

Soot-PCF: Pore condensation and freezing framework for soot aggregates

Soot-PCF: Pore condensation and freezing framework for soot aggregates

Soot PCF: pore condensation and freezing framework for soot aggregates

Spontaneous Imbibition in a Square Tube With Corner Films: Theoretical Model and Numerical Simulation

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