Numerical simulations of axisymmetric adiabatic flow past a gravitating solid sphere

Matsuda, Takuya; Sekino, Nobuhiro; Shima, Eiji; Sawada, Keisuke

doi:10.1093/mnras/236.4.817

Cited by 5 publications

(5 citation statements)

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“…Compared with the ∆z/r s = 0.2 model, the model with ∆z/r s = 0.1 presents the shock oscillations with higher amplitudes and arrives at quasi-steady equilibrium earlier. This resolution dependence of the shock oscillations was also noticed by Matsuda et al (1989) for adiabatic BHL flows onto an absorbing perturber. The resolution study shown in Figure 17 suggests that our numerical results for the DF forces are reliable as long as 5 or more grids per r s are taken.…”

Section: Resolution Dependencysupporting

confidence: 77%

“…The different boundary conditions might lead to different evolution and structure of wakes. For instance, the BHL accretion flows around a perturber present nonlinear features including a detached bow shock, vortex oscillations, and counterstreams in the forward/backward directions, just as in our models, if the perturber is not perfectly absorbing (Shima et al 1985;Fryxell et al 1987;Matsuda et al 1989). When the perturber has a totally absorbing surface, on the other hand, the wakes are relatively quiescent, flowing nearly spherically into the perturber that absorbs the angular momentum carried by the accreting gas (Shima et al 1985;Fryxell et al 1987;Koide et al 1991;Ruffert 1994).…”

Section: Summary and Discussionmentioning

confidence: 55%

“…Despite these differences, the detached distances of bow shocks and the resulting DF forces appear to be not so sensitive to the boundary conditions adopted. Figure 18 plots the detached shock distances inferred from the results of two-dimensional axisymmetric simulations (Shima et al 1985;Fryxell et al 1987;Matsuda et al 1989;Koide et al 1991) and the tabulated values from three-dimensional nonaxisymmetric runs (Ruffert 1994) for the BHL accretion flows, by taking r s equal to the radius of the perturber. The BHL results under the reflecting boundary conditions are larger than our results by a factor of only ∼ 1.2, while those under the absorbing boundary conditions are smaller by a factor of ∼ 0.4.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…It was Hunt (1971Hunt ( , 1979 who first solved for BHL accretion flows numerically, finding that the collisional nature of gas supports a bow shock in front of a supersonic perturber. Later studies found that the BHL accretion flows exhibit unstable behaviors such as flip-flop motions of the accretion shocks and vortex shedding when the condition of axisymmetry is relaxed (e.g., Matsuda et al 1987;Matsuda et al 1989;Ruffert 1994;Foglizzo & Ruffert 1997Foglizzo et al 2005). While these numerical works on the BHL accretion explored temporal evolution and distribution of density wakes as well as nonlinear features in some great detail, they mainly concentrated on the gravitational focusing and resulting accretion rate of gas onto the perturber.…”

Section: Introductionmentioning

confidence: 99%

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Nonlinear Dynamical Friction in a Gaseous Medium

Kim

2009

ApJ

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Using high-resolution, two-dimensional hydrodynamic simulations, we investigate nonlinear gravitational responses of gas to, and the resulting drag force on, a very massive perturber M p moving at velocity V p through a uniform gaseous medium of adiabatic sound speed a ∞ . We model the perturber as a Plummer potential with softening radius r s , and run various models with differing A = GM p /(a 2 ∞ r s ) and M = V p /a ∞ by imposing cylindrical symmetry with respect to the line of perturber motion. For supersonic cases, a massive perturber quickly develops nonlinear flows that produce a detached bow shock and a vortex ring, which is unlike in the linear cases where Mach cones are bounded by low-amplitude Mach waves. The flows behind the shock are initially non-steady, displaying quasi-periodic, overstable oscillations of the vortex ring and the shock. The vortex ring is eventually shed downstream and the flows evolve toward a quasi-steady state where the density wake near the perturber is in near hydrostatic equilibrium. We find that the detached shock distance δ and the nonlinear drag force F depend solely on η = A/(M 2 − 1) such that δ/r s = η and F/F lin = (η/2) −0.45 for η > 2, where F lin is the linear drag force of Ostriker (1999). The reduction of F compared with F lin is caused by front-back symmetry in the nonlinear density wakes. In subsonic cases, the flows without involving a shock do not readily reach a steady state. Nevertheless, the subsonic density wake near a perturber is close to being hydrostatic, resulting in the drag force similar to the linear case. Our results suggest that dynamical friction of a very massive object as in a merger of black holes near a galaxy center will take considerably longer than the linear prediction.

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Section: Resolution Dependencysupporting

confidence: 77%

Section: Summary and Discussionmentioning

confidence: 55%

Section: Summary and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Nonlinear Dynamical Friction in a Gaseous Medium

Kim

2009

ApJ

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“…Here we exclude simulations with a non-absorbing or not fully absorbing accretor, such asFryxell et al (1987) andMatsuda et al (1989).MNRAS 000, 000-000 (0000)…”

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confidence: 99%

Bondi–Hoyle–Lyttleton accretion in supergiant X-ray binaries: stability and disc formation

Stone

2019

Monthly Notices of the Royal Astronomical Society

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We use 2D (axisymmetric) and 3D hydrodynamic simulations to study Bondi-Hoyle-Lyttleton (BHL) accretion with and without transverse upstream gradients. We mainly focus on the regime of high (upstream) Mach number, weak upstream gradients and small accretor size, which is relevant to neutron star (NS) accretion in wind-fed Supergiant X-ray binaries (SgXBs). We present a systematic exploration of the flow in this regime. When there are no upstream gradients, the flow is always stable regardless of accretor size or Mach number. For finite upstream gradients, there are three main types of behavior: stable flow (small upstream gradient), turbulent unstable flow without a disk (intermediate upstream gradient), and turbulent flow with a disk-like structure (relatively large upstream gradient). When the accretion flow is turbulent, the accretion rate decreases non-convergently as the accretor size decreases. The flow is more prone to instability and the disk is less likely to form than previously expected; the parameters of most observed SgXBs place them in the regime of a turbulent, diskless accretion flow. Among the SgXBs with relatively well-determined parameters, we find OAO 1657-415 to be the only one that is likely to host a persistent disk (or disk-like structure); this finding is consistent with observations. c 0000 The Authors arXiv:1907.06108v1 [astro-ph.HE] 13 Jul 2019 R , v Φ ) is evaluated in the rotating frame in which the binary is fixed. D = a b − Rc is the separation between the NS and the surface of the companion (assuming circular orbit). ρ,v are the transverse gradients of density and velocity for single-star wind profile at the NS, and physically correspond to the fractional change of ρ, v per Ra (see text for detailed definition). Ra/R H characterizes the importance of the companion's gravity (with R H being the Hill sphere radius), and Ω b ta characterizes the importance of Coriolis force. The last five parameters show how significantly the system differs from axisymmetric BHL accretion.

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Plasma Physics of Accreting Neutron Stars

Ghosh

Lamb

1991

Neutron Stars: Theory and Observation

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Numerical simulations of axisymmetric adiabatic flow past a gravitating solid sphere

Cited by 5 publications

References 0 publications

Nonlinear Dynamical Friction in a Gaseous Medium

Nonlinear Dynamical Friction in a Gaseous Medium

Bondi–Hoyle–Lyttleton accretion in supergiant X-ray binaries: stability and disc formation

Plasma Physics of Accreting Neutron Stars

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