Model-free kinetics applied to volatilization of Brazilian sunflower oil, and its respective biodiesel

Santos, Anne Gabriella Dias; Araújo, Antônio S.; Caldeira, Vinícius Patrício da Silva; Fernandes, Valter J.; Souza, Luíz Di; Barros, Allan Kardec

doi:10.1016/j.tca.2010.04.015

Cited by 45 publications

(24 citation statements)

References 16 publications

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“…Although in the Ohmic regime unstratified and stratified simulations tend to yield similar criterion (Sano et al 1998;Fleming et al 2000;Turner et al 2007), it is yet to be explored whether the same situation holds for the case of ambipolar diffusion. In addition, above the MRI active layer, magnetic dissipation may generate a hot disk corona, which on the one hand, possesses some stress (although much smaller than that in the active layer, Miller & Stone 2000), and on the other hand, increases β in the upper disk.…”

Section: Recombination Timementioning

confidence: 99%

Magnetorotational-Instability-Driven Accretion in Protoplanetary Disks

Bai

2011

ApJ

180

166

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Non-ideal MHD effects play an important role in the gas dynamics in protoplanetary disks (PPDs). This paper addresses its influence on the magnetorotational instability (MRI) and angular momentum transport in PPDs using the most up-to-date results from numerical simulations. We perform chemistry calculations using a complex reaction network with standard prescriptions for X-ray and cosmic-ray ionizations. We first show that no matter grains are included or not, the recombination time is at least one order of magnitude less than the orbital time within 5 disk scale heights, justifying the validity of local ionization equilibrium and strong coupling limit in PPDs. The full conductivity tensor at different disk radii and heights is evaluated, with the MRI active region determined by requiring that (1) the Ohmic Elsasser number Λ be greater than 1; (2) the ratio of gas to magnetic pressure β be greater than β min (Am) as identified in the recent study by Bai & Stone (2011), where Am is the Elsasser number for ambipolar diffusion. With full flexibility as to the magnetic field strength, we provide a general framework for estimating the MRI-driven accretion rateṀ and the magnetic field strength in the MRI-active layer. We find that the MRI-active layer always exists at any disk radius as long as the magnetic field in PPDs is sufficiently weak. However, the optimistically predictedṀ in the inner disk (r = 1 − 10 AU) appears insufficient to account for the observed range of accretion rate in PPDs (around 10 −8 M ⊙ yr −1 ) even in the grain-free calculation, and the presence of solar abundance sub-micron grains further reducesṀ by one to two orders of magnitude. Moreover, we find that the predictedṀ increases with radius in the inner disk where accretion is layered, which would lead to runaway mass accumulation if disk accretion is solely driven by the MRI. Our results suggest that stronger sources of ionization, and/or additional mechanisms such as magnetized wind are needed to explain the observed accretion rates in PPDs. In contrast, our predictedṀ is on the order of 10 −9 M ⊙ yr −1 in the outer disk, consistent with the observed accretion rates in transitional disks.

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Section: Recombination Timementioning

confidence: 99%

Magnetorotational-Instability-Driven Accretion in Protoplanetary Disks

Bai

2011

ApJ

180

166

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“…In the ADAF, the matter moves to the central object with a speed comparable to the free-fall velocity (v ff ) (v f ∼ αv ff ; Narayan & Yi 1995). If the optical fluctuations, which were triggered at a region close to the truncation radius, propagated to the central black hole via the accretion of mass flow on the free-fall timescale in the ADAF, the transition radius is estimated to be ∼2.5-4.0×10 8 [cm] by using the above approximation for α = 0.01 (Sano et al 1998;Machida & Matsumoto 2003) and our estimates of X-ray delays. The estimated value of R tr corresponds to ∼100-150r s .…”

Section: Time Delay Caused By Propagation Of Mass Accretion Flow In Tmentioning

confidence: 99%

Rapid optical variations correlated with X-rays in the 2015 second outburst of V404 Cygni (GS 2023+338)

Kimura

Katô

Isogai

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present optical multi-colour photometry of V404 Cyg during the outburst from December, 2015 to January, 2016 together with the simultaneous X-ray data. This outburst occurred less than 6 months after the previous outburst in June-July, 2015. These two outbursts in 2015 were of a slow rise and rapid decay-type and showed large-amplitude (∼2 mag) and short-term (∼10 min-3 hours) optical variations even at low luminosity (0.01-0.1L Edd ). We found correlated optical and X-ray variations in two ∼1 hour time intervals and obtained a Bayesian estimate of an X-ray delay against the optical emission, which is ∼30-50 s, during those two intervals. In addition, the relationship between the optical and X-ray luminosity was L opt ∝ L 0.25−0.29 X at that time. These features cannot be easily explained by the conventional picture of transient black-hole binaries, such as canonical disc reprocessing and synchrotron emission related to a jet. We suggest that the disc was truncated during those intervals and that the X-ray delays represent the required time for propagation of mass accretion flow to the inner optically-thin region with a speed comparable to the free-fall velocity.

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“…The linear growth rate of the MRI can be reduced significantly because of the suppression by ohmic dissipation. Two-and three-dimensional local shearing box simulations (Sano et al 1998(Sano et al , 2004Sano & Stone 2002) have shown that physical properties of the saturated turbulence depend on the Lundquist number S MRI v 2 A /, where v A is the Alfvén velocity, is the angular velocity, and is the magnetic diffusivity (see also Fleming et al 2000;Ziegler & Rüdiger 2001;Liu et al 2006). Particularly, when S MRI T1, the size of the saturated stress decreases with the decrease of S MRI (Sano & Stone 2002;Pessah et al 2007).…”

Section: Introductionmentioning

confidence: 99%

Axisymmetric Magnetorotational Instability in Viscous Accretion Disks

Masada

Sano

2008

Astrophysical Journal

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Axisymmetric magnetorotational instability (MRI) in viscous accretion disks is investigated by linear analysis and two-dimensional nonlinear simulations. The linear growth of the viscous MRI is characterized by the Reynolds number defined as R MRI v 2 A /, where v A is the Alfvén velocity, is the kinematic viscosity, and is the angular velocity of the disk. Although the linear growth rate is suppressed considerably as the Reynolds number decreases, the nonlinear behavior is found to be almost independent of R MRI . At the nonlinear evolutionary stage, a two-channel flow continues growing and the Maxwell stress increases until the end of calculations even though the Reynolds number is much smaller than unity. A large portion of the injected energy to the system is converted to the magnetic energy. The gain rate of the thermal energy, on the other hand, is found to be much larger than the viscous heating rate. Nonlinear behavior of the MRI in the viscous regime and its difference from that in the highly resistive regime can be explained schematically by using the characteristics of the linear dispersion relation. Applying our results to the case with both the viscosity and resistivity, it is anticipated that the critical value of the Lundquist number S MRI v 2 A / for active turbulence depends on the magnetic Prandtl number S MRI;c / Pm 1 = 2 in the regime of Pm 31 and remains constant when PmT1, where Pm S MRI /R MRI ¼ / and is the magnetic diffusivity.

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Model-free kinetics applied to volatilization of Brazilian sunflower oil, and its respective biodiesel

Cited by 45 publications

References 16 publications

Magnetorotational-Instability-Driven Accretion in Protoplanetary Disks

Magnetorotational-Instability-Driven Accretion in Protoplanetary Disks

Rapid optical variations correlated with X-rays in the 2015 second outburst of V404 Cygni (GS 2023+338)

Axisymmetric Magnetorotational Instability in Viscous Accretion Disks

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