Thermal conductivity and coordination number of compressed dust aggregates

Arakawa, Sota; Tatsuuma, Misako; Sakatani, Naoya; Nakamoto, Taishi

doi:10.1016/j.icarus.2019.01.022

Cited by 19 publications

(18 citation statements)

References 33 publications

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“…According to empirical relationships between the coordination number and the packing fraction for aggregates of spherical particles [15,16,26] (Fig. 7), the packing fraction of ~0.3 corresponds to an average coordination number of ~3-5, which is consistent with numerical results [14].…”

Section: Resultssupporting

confidence: 84%

Packing fraction of clusters formed in free-falling granular streams based on flash x-ray radiography

et al. 2021

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We study the packing fraction of clusters in free-falling streams of spherical and irregularly shaped particles using flash X-ray radiography. The estimated packing fraction of clusters is low enough to correspond to coordination numbers less than 6. Such coordination numbers in numerical simulations correspond to aggregates that collide and grow without bouncing. Moreover, the streams of irregular particles evolved faster and formed clusters of larger sizes with lower packing fraction. This result on granular streams suggests that particle shape has a significant effect on the agglomeration process of granular materials.

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Section: Resultssupporting

confidence: 84%

Packing fraction of clusters formed in free-falling granular streams based on flash x-ray radiography

et al. 2021

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“…(D.4) Therefore, F Ph /F D is independent of a for the case of a < l m , while F Ph /F D is inversely proportional to the square of the particle radius for the case of a > l m This means that the radial drift of cm-sized compact pebbles could not be prevented by photophoresis itself, although the radial drift would be stopped because the pressure maximum formed at the light barrier. We note, however, that the thermal conductivity of dust aggregates is exceedingly lower than that of compact dust particles (e.g., Arakawa et al 2017Arakawa et al , 2019, and the radial drift of aggregated pebbles might be stopped by photophoresis, even if their radius is larger than the mean free path of the gas molecules. Temperature T [K] p = 10 0 dyn cm -2 p = 10 2 dyn cm -2 p = 10 4 dyn cm -2 p = 10 6 dyn cm -2 fitting 10 -5 10 -4 10 -3 10 -2 10 -1 10 0 10 1 10 2 10 2 10 3 where c p = 10 7 erg g −1 K −1 is the specific heat (e.g., Ciesla et al 2004).…”

Section: Appendix D: Mean Free Path Of Gas Moleculesmentioning

confidence: 73%

Photophoresis in the circumjovian disk and its impact on the orbital configuration of the Galilean satellites

Arakawa

Shibaike

2019

A&A

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Jupiter has four large regular satellites called the Galilean satellites: Io, Europa, Ganymede, and Callisto. The inner three of the Galilean satellites orbit in a 4:2:1 mean motion resonance; therefore their orbital configuration may originate from the stopping of the migration of Io near the bump in the surface density distribution and following resonant trapping of Europa and Ganymede. The formation mechanism of the bump near the orbit of the innermost satellite, Io, is not yet understood, however. Here, we show that photophoresis in the circumjovian disk could be the cause of the bump, using analytic calculations of steady-state accretion disks. We propose that photophoresis in the circumjovian disk could stop the inward migration of dust particles near the orbit of Io. The resulting dust depleted inner region would have a higher ionization fraction, and thus admit increased magnetorotational-instabilitydriven accretion stress than the outer region. The increase of the accretion stress at the photophoretic dust barrier would form a bump in the surface density distribution, halting the migration of Io.

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“…The aggregation of monomers formed with a larger geometric diameter and wider distribution as the increase in the volume fraction, which means that the polydisperse of coagulation is higher with the denser system. Teichmann and Van also found that the coordination number (i.e., the average number of contacts per monomer) increases with the compression of aggregates [41]. Figure 10 shows the power-law relationship between the radius of gyrations a number of monomers in each aggregate under stable conditions.…”

Section: Cluster Analysis Of Collision Particlesmentioning

confidence: 89%

Polymerization and Collision in High Concentrations for Brownian Coagulation

Wang

Liu

et al. 2021

Applied Sciences

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Aggregation always occurs in industrial processes with fractal-like particles, especially in dense systems (the volume fraction, ϕ>1%). However, the classic aggregation theory, established by Smoluchowski in 1917, cannot sufficiently simulate the particle dynamics in dense systems, particularly those of generat ed fractal-like particles. In this article, the Langevin dynamic was applied to study the collision rate of aggregations as well as the structure of aggregates affected by different volume fractions. It is shown that the collision rate of highly concentrated particles is progressively higher than that of a dilute concentration, and the SPSD (self-preserving size distribution) is approached (σg,n≥1.5). With the increase in volume fraction, ϕ, the SPSD broadens, and the geometric standard is 1.54, 1.98, and 2.73 at ϕ= 0.1, 0.2, and 0.3. When the volume fraction, ϕ, is higher, the radius of gyration is smaller with the same cluster size (number-based), which means the particle agglomerations are in a tighter coagulation. The fractal-like property Df is in the range of 1.60–2.0 in a high-concentration system. Knowing the details of the collision progress in a high-concentration system can be useful for calculating the dynamics of coagulating fractal-like particles in the industrial process.

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Thermal conductivity and coordination number of compressed dust aggregates

Cited by 19 publications

References 33 publications

Packing fraction of clusters formed in free-falling granular streams based on flash x-ray radiography

Packing fraction of clusters formed in free-falling granular streams based on flash x-ray radiography

Photophoresis in the circumjovian disk and its impact on the orbital configuration of the Galilean satellites

Polymerization and Collision in High Concentrations for Brownian Coagulation

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