Properties of Accretion Shocks in Viscous Flows With Cooling Effects

Das, Santabrata; Chakrabarti, Sandip K.

doi:10.1142/s0218271804005912

Cited by 26 publications

(9 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Furthermore, many authors have pointed out that shocks may undergo radial, vertical or non‐axisymmetrical oscillations (Molteni, Toth & Kuznetsov 1999; Gu & Foglizzo 2003), although they are generally never ruined by these oscillations. In Das & Chakrabarti (2004), bremsstrahlung cooling was also added, bearing in mind that it is a very inefficient cooling process (Chattopadhyay & Chakrabarti 2000), and a complete set of global solutions of viscous transonic flow with and without shocks was presented. The hot and dense post‐shock flow, which basically acts as a ‘boundary layer’ for the black holes, could be the natural site of hot radiation in accretion discs.…”

Section: Introductionmentioning

confidence: 99%

Behaviour of dissipative accretion flows around black holes

Das¹

2007

Monthly Notices of the Royal Astronomical Society

Self Cite

View full text Add to dashboard Cite

We investigate the behaviour of dissipative accreting matter close to a black hole as it provides the important observational features of galactic and extra-galactic black holes candidates. We find the complete set of global solutions in presence of viscosity and synchrotron cooling. We show that advective accretion flow can have standing shock wave and the dynamics of the shock is controlled by the dissipation parameters (both viscosity and cooling). We study the effective region of the parameter space for standing as well as oscillating shock. We find that shock front always moves towards the black hole as the dissipation parameters are increased. However, viscosity and cooling have opposite effects in deciding the solution topologies. We obtain two critical cooling parameters that separate the nature of accretion solution.Comment: 11 pages, 11 figures, submitted to MNRA

show abstract

Section: Introductionmentioning

confidence: 99%

Behaviour of dissipative accretion flows around black holes

Das¹

2007

Monthly Notices of the Royal Astronomical Society

Self Cite

View full text Add to dashboard Cite

show abstract

“…It has been shown by Chakrabarti (1989) that low angular momentum, non‐dissipative flows produce axisymmetric standing shock waves in tens of Schwarzschild radii, but the presence of a large viscosity (Chakrabarti 1990, hereafter C90) will remove the shock wave since the Rankine–Hugoniot relation is not satisfied in a highly dissipative flow. A confirmation of such an assertion, originally made in the context of the isothermal flows, came both through numerical simulations (Chakrabarti & Molteni 1995, hereafter CM95) and theoretical studies of flows with a more general equation of states (Chakrabarti 1996a, hereafter C96; Chakrabarti & Das 2004; Das & Chakrabarti 2004). The theoretical works showed that the topology of the flow is modified when viscosity is added, and beyond a critical viscosity, the centrifugal pressure supported shocks do not form.…”

Section: Introductionmentioning

confidence: 85%

Hydrodynamic simulations of viscous accretion flows around black holes

Giri

Chakrabarti

2012

Monthly Notices of the Royal Astronomical Society

Self Cite

View full text Add to dashboard Cite

We study the time evolution of a rotating, axisymmetric, viscous accretion flow around black holes using a grid based finite difference method. We use the Shakura-Sunyaev viscosity prescription. However, we compare with the results obtained when all the three independent components of the viscous stress are kept. We show that the centrifugal pressure supported shocks became weaker with the inclusion of viscosity. The shock is formed farther out when the viscosity is increased. When the viscosity is above a critical value, the shock disappears altogether and the flow becomes subsonic and Keplerian everywhere except in a region close to the horizon, where it remains supersonic. We also find that as the viscosity is increased, the amount of outflowing matter in the wind is decreased to less than a percentage of the inflow matter. Since the post-shock region could act as a reservoir of hot electrons or the so-called 'Compton cloud', the size of which changes with viscosity, the spectral properties are expected to depend on viscosity strongly: the harder states are dominated by low-angular momentum and the low viscosity flow with a significant outflows while the softer states are dominated by the high viscosity Keplerian flow having very little outflows.Comment: 21 pages, 11 fiures, Accepted in MNRAS (In Press

show abstract

“…2,15 It would be interesting to study how the dissipative processes modify the shape of the duct. Particularly important is the fact that above a critical viscosity the standing shock itself disappears.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

Accretion Onto Compact Objects Viewed as a Flow in Converging-Diverging Ducts

Chakrabarti

Majumdar

Chakrabarti

2008

Int. J. Mod. Phys. D

Self Cite

View full text Add to dashboard Cite

Black hole accretion is necessarily transonic and the number of physical sonic points depends on the angular momentum of the flow. We study the properties of such a flow by recasting this idea into an engineering problem in which a flow has a subsonic to supersonic transition when it passes through a de Laval nozzle, i.e. a converging and diverging duct in a flat geometry in the presence of sufficient end pressure difference. Particularly interesting is the case of the centrifugal pressure supported standing shock formation inside an accretion flow, because the flow passes through at least two saddle type sonic points, one before and one after the shock. In this case, the duct itself has two minima and a maximum. We study the properties of such a duct as a function of the inflow parameters and classify all possible types of the flow through this composite nozzle.

show abstract

Properties of Accretion Shocks in Viscous Flows With Cooling Effects

Cited by 26 publications

References 12 publications

Behaviour of dissipative accretion flows around black holes

Behaviour of dissipative accretion flows around black holes

Hydrodynamic simulations of viscous accretion flows around black holes

Accretion Onto Compact Objects Viewed as a Flow in Converging-Diverging Ducts

Contact Info

Product

Resources

About