Radial Flow of Dust Particles in Accretion Disks

Takeuchi, Taku; Lin, D. N. C.

doi:10.1086/344437

Cited by 403 publications

(469 citation statements)

References 16 publications

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“…Hence, the reversal of the radial flow profile compared to the usual α-model is a clear consequence of the anisotropy. This will have an effect on the dust migration processes (Stoll & Kley 2016) that need to be contrasted to the outward drift in the midplane viscous models (Takeuchi & Lin 2002). From this we can conclude that we need to be careful with turbulence models imposed on accretions disks when we adopt viscous models to describe them.…”

Section: Discussionmentioning

confidence: 99%

Anisotropic hydrodynamic turbulence in accretion disks

Stoll

Kley

Picogna

2017

A&A

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Recently, the vertical shear instability (VSI) has become an attractive purely hydrodynamic candidate for the anomalous angular momentum transport required for weakly ionized accretion disks. In direct three-dimensional numerical simulations of VSI turbulence in disks, a meridional circulation pattern was observed that is opposite to the usual viscous flow behavior. Here, we investigate whether this feature can possibly be explained by an anisotropy of the VSI turbulence. Using three-dimensional hydrodynamical simulations, we calculate the turbulent Reynolds stresses relevant for angular momentum transport for a representative section of a disk. We find that the vertical stress is significantly stronger than the radial stress. Using our results in viscous disk simulations with different viscosity coefficients for the radial and vertical direction, we find good agreement with the VSI turbulence for the stresses and meridional flow; this provides additional evidence for the anisotropy. The results are important with respect to the transport of small embedded particles in disks.

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Section: Discussionmentioning

confidence: 99%

Anisotropic hydrodynamic turbulence in accretion disks

Stoll

Kley

Picogna

2017

A&A

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“…The negative sign indicates an inward flow. When considering the 2D structure of disks within the α-turbulence framework, it can be shown (e.g., Takeuchi & Lin 2002) that for most commonly used power-law relations for the density and temperature radial profiles, a meridional circulation sets in that maintains a strong, inward flow in the upper layers of the disk and a weaker outward flow in the mid-plane. The density-averaged flow still obeys Eq.…”

Section: Rate and Geometry Of Gas Accretionmentioning

confidence: 99%

“…(62a) and (62b) to the 3D case, and neglecting variations of the gas and dust velocity with height in the disk (see Takeuchi & Lin 2002), we can express the approach velocities between an inclined planetesimal and dust as…”

Section: Including Inclinationsmentioning

confidence: 99%

On the filtering and processing of dust by planetesimals

Guillot

Ida

Ormel

2014

A&A

141

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Context. Circumstellar disks are known to contain a significant mass in dust ranging from micron to centimeter size. Meteorites are evidence that individual grains of those sizes were collected and assembled into planetesimals in the young solar system. Aims. We assess the efficiency of dust collection of a swarm of non-drifting planetesimals with radii ranging from 1 to 10 3 km and beyond. Methods. We calculate the collision probability of dust drifting in the disk due to gas drag by planetesimal accounting for several regimes depending on the size of the planetesimal, dust, and orbital distance: the geometric, Safronov, settling, and three-body regimes. We also include a hydrodynamical regime to account for the fact that small grains tend to be carried by the gas flow around planetesimals. Results. We provide expressions for the collision probability of dust by planetesimals and for the filtering efficiency by a swarm of planetesimals. For standard turbulence conditions (i.e., a turbulence parameter α = 10 −2 ), filtering is found to be inefficient, meaning that when crossing a minimum-mass solar nebula (MMSN) belt of planetesimals extending between 0.1 AU and 35 AU most dust particles are eventually accreted by the central star rather than colliding with planetesimals. However, if the disk is weakly turbulent (α = 10 −4 ) filtering becomes efficient in two regimes: (i) when planetesimals are all smaller than about 10 km in size, in which case collisions mostly take place in the geometric regime; and (ii) when planetary embryos larger than about 1000 km in size dominate the distribution, have a scale height smaller than one tenth of the gas scale height, and dust is of millimeter size or larger in which case most collisions take place in the settling regime. These two regimes have very different properties: we find that the local filtering efficiency x filter,MMSN scales with r −7/4 (where r is the orbital distance) in the geometric regime, but with r −1/4 to r 1/4 in the settling regime. This implies that the filtering of dust by small planetesimals should occur close to the central star and with a short spread in orbital distances. On the other hand, the filtering by embryos in the settling regime is expected to be more gradual and determined by the extent of the disk of embryos. Dust particles much smaller than millimeter size tend only to be captured by the smallest planetesimals because they otherwise move on gas streamlines and their collisions take place in the hydrodynamical regime. Conclusions. Our results hint at an inside-out formation of planetesimals in the infant solar system because small planetesimals in the geometrical limit can filter dust much more efficiently close to the central star. However, even a fully-formed belt of planetesimals such as the MMSN only marginally captures inward-drifting dust and this seems to imply that dust in the protosolar disk has been filtered by planetesimals even smaller than 1 km (not included in this study) or that it has been assembled into planetesi...

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“…We compare the drift speed of a test particle with the analytical results of Takeuchi & Lin (2002). If the gas density profile is constant over the radius and the temperature profile follows T (r) ∝ r −1 , the radial drift velocity of the particle relative to that of the gas (Δv r ) can be given as…”

Section: Testsmentioning

confidence: 99%

The first stages of planet formation in binary systems: how far can dust coagulation proceed?

Zsom

Sándor

Dullemond

2011

A&A

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Context. On the basis of current theoretical models, giant planets can form via gravitational instability or core accretion. The terrestrial planets are "failed cores" in the core accretion paradigm that do not evolve into gas giants. Planets residing in binary systems place strong constraints on planet formation theory as any model must work in binary systems too, in spite of the strong perturbations from the secondary star. Aims. We examine the first phase of the core accretion model, namely the dust growth/fragmentation in binary systems. In our model, a gas and dust disk exists around the primary star and is perturbed by the secondary. We study the effects of a secondary with/without eccentricity on the dust population to determine the sizes the aggregates can reach and how that compares to the dust population in disks around single stars. Methods. We solve the equation of motion of dust aggregates including gas drag and gravitational forces from both stars, as well as the hydrodynamical equations for the gas disk. We determine the velocity of these particles relative to the gas (or relative to micronsized, well-coupled dust particles) and construct a collision model with growth and erosion. Particles below the critical fragmentation velocity increase in mass by sweeping up the small dust population; particles above this critical speed are eroded by collisions with the small dust population. We use this model to determine the sizes that aggregates can reach in the disk, in addition to the equilibrium mass and stopping time distributions between growth and erosion. Results. We find that the secondary star has two effects on the dust population: 1. the disk is truncated because of the presence of the secondary star, and the maximum mass of the particles is lower in lower gas densities. This effect is predominant in the outer disk; 2. the perturbation of the secondary increases the eccentricity of the gas disk, which in turn increases the relative velocity between the dust and the gas. Hence the maximum particle sizes are further decreased. The second effect of the secondary influences the entire disk. Coagulation is efficiently reduced even at the very inner parts of the disk. The average mass of the particles is lower by four orders of magnitude (as a consequence, the stopping time is shorter by one order of magnitude) in disks around binary systems than for dust in disks around single stars.

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Radial Flow of Dust Particles in Accretion Disks

Cited by 403 publications

References 16 publications

Anisotropic hydrodynamic turbulence in accretion disks

Anisotropic hydrodynamic turbulence in accretion disks

On the filtering and processing of dust by planetesimals

The first stages of planet formation in binary systems: how far can dust coagulation proceed?

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