A Numerical Study of Viscous Flows in Axisymmetric alpha -Accretion Disks

Rozyczka, M.; Bodenheimer, Peter; Bell, K. R.

doi:10.1086/173853

Cited by 39 publications

(42 citation statements)

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“…Kley & Lin (1992) found backflows near the midplane, similar to Urpin's solutions, but have shown that if an inflow condition at the outer boundary is assumed, a circulation pattern is obtained. More detailed studies by Różyczka et al (1994) also exhibited flows with regions of midplane backflows and with circulation patterns. Kluźniak & Kita (1997), hereafter KK, in a beautiful work, carried out expansions in up to second order and considered the full viscous flow dynamics, but neglected thermal effects (which Urpin retained).…”

Section: Introductionmentioning

confidence: 89%

Asymptotic models of meridional flows in thin viscous accretion disks

Regev

Gitelman

2002

A&A

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Abstract. We present the results of numerical integrations yielding the structure of and meridional flow in axisymmetric thin viscous accretion disk models. The solutions are obtained by simplifying and approximating first the equations, using systematic asymptotic expansions in the small parameter , measuring the relative disk thickness. The vertical structure is solved including radiative transfer in the diffusion approximation. Carrying out the expansion to second order in we obtain, for low enough values of the viscosity parameter α, solutions containing backflows. These solutions are similar to the results first found by Urpin (1984), who used approximations that are only valid for large radii and the asymptotic analytical solutions of Kluźniak & Kita (1997), valid only for polytropic disks. Our results may be important for several outstanding issues in accretion disk theory.

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Section: Introductionmentioning

confidence: 89%

Asymptotic models of meridional flows in thin viscous accretion disks

Regev

Gitelman

2002

A&A

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“…This process is typically much weaker than radial drift and thus unable to explain millimeter sized particles in the outer disk. In addition, large-scale circulation pattern of meridional flows, while present in viscous disk simulations (Kley and Lin, 1992;Rozyczka et al, 1994), are not reproduced in MRI turbulent simulations (Fromang et al, 2011).…”

Section: Radial Mixing and Meridional Flowsmentioning

confidence: 99%

“…The use of the sub-millimeter spectral index as a probe of the grain size distribution has been questioned by several studies which showed a possible dependence of the dust opacity with temperature (Paradis et al, 2010;Veneziani et al, 2010). However, recent detailed studies of dense and cold clouds which include a broader range of (sub-)millimeter wavelengths, suggest that, in some cases, the observed anti-correlation between the dust opacity spectral index β and temperature may be the result of the uncertainties resulting from using simplified single temperature modified black body fits to observations covering a limited range of wavelengths (Shetty et al, 2009;Kelly et al, 2012;Sadavoy et al, 2013;Juvela et al, 2013). Indirect evidence supporting grain growth in the dense regions of prestellar cores has been obtained by Keto and Caselli (2008), which invoke significant grain growth at densities exceeding 10 5 cm −3 to explain the inferred change in dust opacity in the inner regions of the studied pre-stellar cores.…”

Section: Dust Evolution Before the Disk For-mationmentioning

confidence: 99%

Dust Evolution in Protoplanetary Disks

Testi¹,

Birnstiel²,

Ricci³

et al. 2014

Protostars and Planets VI

293

271

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In the core accretion scenario for the formation of planetary rocky cores, the first step toward planet formation is the growth of dust grains into larger and larger aggregates and eventually planetesimals. Although dust grains are thought to grow from the submicron sizes typical of interstellar dust to micron size particles in the dense regions of molecular clouds and cores, the growth from micron size particles to pebbles and kilometre size bodies must occur in the high densities reached in the mid-plane of protoplanetary disks. This critical step in the formation of planetary systems is the last stage of solids evolution that can be observed directly in young extrasolar systems before the appearance of large planetary-size bodies.Tracing the properties of dust in the disk mid-plane, where the bulk of the material for planet formation resides, requires sensitive observations at long wavelengths (sub-mm through cm waves). At these wavelengths, the observed emission can be related to the dust opacity, which in turns depend on to the grain size distribution. In recent years the upgrade of the existing (sub-)mm arrays, the start of ALMA Early Science operations and the upgrade of the VLA have significantly improved the observational constraints on models of dust evolution in protoplanetary disks. Laboratory experiments and numerical simulations led to a substantial improvement in the understanding of the physical processes of grain-grain collisions, which are the foundation for the models of dust evolution in disks.In this chapter we review the constraints on the physics of grain-grain collisions as they have emerged from laboratory experiments and numerical computations. We then review the current theoretical understanding of the global processes governing the evolution of solids in protoplanetary disks, including dust settling, growth, and radial transport. The predicted observational signatures of these processes are summarized.We discuss the recent developments in the study of grain growth in molecular cloud cores and in collapsing envelopes of protostars as these likely provide the initial conditions for the dust in protoplanetary disks. We then discuss the current observational evidence for the growth of grains in young protoplanetary disks from millimeter surveys, as well as the very recent evidence of radial variations of the dust properties in disks. We also include a brief discussion of the constraints on the small end of the grain size distribution and on dust settling as derived from optical, near-, and mid-IR observations. The observations are discussed in the context of global dust evolution models, in particular we focus on the emerging evidence for a very efficient early growth of grains in disks and the radial distribution of maximum grain sizes as the result of growth barriers in disks. We will also highlight the limits of the current models of dust evolution in disks including the need to slow the radial drift of grains to overcome the migration/fragmentation barrier.

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“…In our viscous simulation, the flow is outward, as shown by the streamlines plotted in Figure 9. The outflow near the midplane-together with inflow in the upper layers-is indeed typical of a 3D viscous-accretion disk (see Urpin 1984;Siemiginowska 1988;Kley & Lin 1992;Rozyczka et al 1994;Regev & Gitelman 2002;Takeuchi & Lin 2002).…”

Section: Flow In the Midplane Of The Circumplanetary Diskmentioning

confidence: 99%

Accretion of Jupiter-Mass Planets in the Limit of Vanishing Viscosity

Szulágyi

Morbidelli

Crida

et al. 2014

ApJ

221

218

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In the core-accretion model, the nominal runaway gas-accretion phase brings most planets to multiple Jupiter masses. However, known giant planets are predominantly Jupiter mass bodies. Obtaining longer timescales for gas accretion may require using realistic equations of states, or accounting for the dynamics of the circumplanetary disk (CPD) in the low-viscosity regime, or both. Here we explore the second way by using global, three-dimensional isothermal hydrodynamical simulations with eight levels of nested grids around the planet. In our simulations, the vertical inflow from the circumstellar disk (CSD) to the CPD determines the shape of the CPD and its accretion rate. Even without a prescribed viscosity, Jupiter's mass-doubling time is ∼10 4 yr, assuming the planet at 5.2 AU and a Minimum Mass Solar Nebula. However, we show that this high accretion rate is due to resolution-dependent numerical viscosity. Furthermore, we consider the scenario of a layered CSD, viscous only in its surface layer, and an inviscid CPD. We identify two planet-accretion mechanisms that are independent of the viscosity in the CPD: (1) the polar inflow-defined as a part of the vertical inflow with a centrifugal radius smaller than two Jupiter radii and (2) the torque exerted by the star on the CPD. In the limit of zero effective viscosity, these two mechanisms would produce an accretion rate 40 times smaller than in the simulation.

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A Numerical Study of Viscous Flows in Axisymmetric alpha -Accretion Disks

Cited by 39 publications

References 0 publications

Asymptotic models of meridional flows in thin viscous accretion disks

Asymptotic models of meridional flows in thin viscous accretion disks

Dust Evolution in Protoplanetary Disks

Accretion of Jupiter-Mass Planets in the Limit of Vanishing Viscosity

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