Theory of Transonic Astrophysical Flows

Chakrabarti, Sandip K.

doi:10.1142/1091

Cited by 269 publications

(466 citation statements)

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“…The SPH method belongs to the so-called "shock-capturing" methods since the role of the artificial viscosity, in inviscid hydrodynamics, is to allow shocks to satisfy the Euler equation when discontinuities (shock or contact discontinuities) are present. In the case of "shock tracking" methods, a complete steady solution requires the equations of energy, angular momentum, and mass conservation to be supplemented by transonic conditions at some critical points and RH conditions at an unknown weak shock location (Chakrabarti 1989(Chakrabarti , 1990). Therefore such methods involve two different codes to solve Euler equations as for inviscid hydrodynamics.…”

Section: The Modelmentioning

confidence: 99%

“…Bondi (1944Bondi ( , 1952 initially studied this kind of phenomena. There is a range of initial values of the flow angular momentum and energy, producing a steady shock, whose position is closer to the BH as decreases the initial angular momentum, as the Rankine-Hugoniot (RH) jump conditions are satisfied (Chakrabarti 1990;Chakrabarti & Molteni 1993;. Physical viscosity, combined together with the angular momentum, produces a shock front capable of pushing out part of the accreting flow from the disc.…”

Section: Introductionmentioning

confidence: 99%

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The role of viscosity in AGN outflows in relation to jet periodicities

Lanzafame¹,

Cassaro

Schillirò

et al. 2008

A&A

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Aims. Adopting the Smoothed Particle Hydrodynamics (SPH) numerical method, we performed a grid of evolving models of a 3D axially-symmetric, viscous accretion disc around a supermassive black hole (SMBH) of 10 6 ÷ 10 9 M . Such sort of simulations are typical of accretion discs in active galactic nuclei (AGN). In such disc models, we pay attention to the role of the specific angular momentum λ and the turbulent viscosity parameter α, according to the Shakura and Sunyaev prescription. One or two shock fronts in the radial inviscid flow develop, according to the assigned initial kinematic and thermodynamic conditions. Methods. By fixing the initial and boundary conditions on the flow at the disc outer edge, where the total energy, the specific angular momentum λ, and the initial velocity are concerned, we find pairs of (α, λ) values determining radial periodical oscillations in the shock front. In some cases, an outflow develops from the subsonic post-shock region, close to the black hole. Results. The link between the accretion disc and the jet refueling through the onset of a centrifugal shock front is evident. We also compare model variability periods with observed ones in the radio light curves of AGN.

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Section: The Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The role of viscosity in AGN outflows in relation to jet periodicities

Lanzafame¹,

Cassaro

Schillirò

et al. 2008

A&A

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“…Comparing these two alternative means of fixing rc, the next logical step would be to say that for the fixed points, and for the solutions passing through them, it should suffice to specify either E orṀ (Chakrabarti 1990). For the two relatively simple cases of disc geometry, i.e.…”

Section: Polytropic Flowsmentioning

confidence: 99%

The role of flow geometry in influencing the stability criteria for low angular momentum axisymmetric black hole accretion

et al. 2012

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Using mathematical formalism borrowed from dynamical systems theory, a complete analytical investigation of the critical behaviour of the stationary flow configuration for the low angular momentum axisymmetric black hole accretion provides valuable insights about the nature of the phase trajectories corresponding to the transonic accretion in the steady state, without taking recourse to the explicit numerical solution commonly performed in the literature to study the multi-transonic black hole accretion disc and related astrophysical phenomena. Investigation of the accretion flow around a non rotating black hole under the influence of various pseudo-Schwarzschild potentials and forming different geometric configurations of the flow structure manifests that the general profile of the parameter space divisions describing the multi-critical accretion is roughly equivalent for various flow geometries. However, a mere variation of the polytropic index of the flow cannot map a critical solution from one flow geometry to the another, since the numerical domain of the parameter space responsible to produce multi-critical accretion does not undergo a continuous transformation in multi-dimensional parameter space. The stationary configuration used to demonstrate the aforementioned findings is shown to be stable under linear perturbation for all kind of flow geometries, black hole potentials, and the corresponding equations of state used to obtain the critical transonic solutions. Finally, the structure of the acoustic metric corresponding to the propagation of the linear perturbation studied are discussed for various flow geometries used.

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“…It may also be the case that transonic flows always result in accretion onto black holes (Chakrabarti, 1990;Kafatos and Yang, 1994) as the inflow speed has to smoothly join the subsonic regime with the supersonic regime near the horizon. It may also be the case that shocks are prevalent (Chakrabarti, 1990;Yang and Kafatos, 1995;Chakrabarti and Titarchuk, 1995;Chakrabarti, 1996). Advection-dominated accretion flows (ADAFs) have been widely discussed in the literature (Narayan and Yi, 1994;Liang and Narayan, 1997;Esin, McClintock, and Narayan, 1997;Narayan, Mahadevan and Quataert, 1999).…”

Section: Thick Disks and Advection-dominated Flowsmentioning

confidence: 99%

Inner Region Accretion Flows Onto Black Holes

Kafatos¹,

Subramanian²

2001

The Neutron Star—Black Hole Connection

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We examine here the inner region accretion flows onto black holes. A variety of models are presented. We also discuss viscosity mechanisms under a variety of circumstances, for standard accretion disks onto galactic black holes and supermassive black holes and hot accretion disks. Relevant work is presented here on unified aspects of disk accretion onto supermassive black holes and the possible coupling of thick disks to beams in the inner regions. We also explore other accretion flow scenarios. We conclude that a variety of scenarios yield high temperatures in the inner flows and that viscosity is likely not higher than alpha ∼ 0.01.

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Theory of Transonic Astrophysical Flows

Cited by 269 publications

References 0 publications

The role of viscosity in AGN outflows in relation to jet periodicities

The role of viscosity in AGN outflows in relation to jet periodicities

The role of flow geometry in influencing the stability criteria for low angular momentum axisymmetric black hole accretion

Inner Region Accretion Flows Onto Black Holes

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