Turbulence modelling in neutron star merger simulations

Radice, David; Hawke, Ian

doi:10.1007/s41115-023-00019-9

Cited by 5 publications

(2 citation statements)

References 125 publications

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“…The maximum value and the overall magnitude of the bulk viscosity is a sensitive function of density through its dependence on the susceptibility factor C 2 /A, see Eq. (7). It decreases with the density, and, e.g., at n B /n 0 = 7 the maximum bulk viscosity is more than an order of magnitude smaller than at n B /n 0 = 4.…”

Section: Bulk Viscosity Of Udse Mattermentioning

confidence: 87%

“…The recent discovery of gravitational waves followed by electromagnetic counterparts originating from binary neutron-star mergers, as observed by the LIGO-Virgo collaboration [1], has spurred interest in the transport characteristics of hot and dense matter. Numerical simulations of binary neutron star mergers typically conducted within the framework of non-dissipative hydrodynamics, have predicted significant density oscillations and robust gravitational wave emissions in the initial tens of milliseconds following the merger [2][3][4][5][6][7]. These oscillations are expected to eventually dissipate due to various dissipative processes within the post-merger matter, ultimately impacting the gravitational wave signal.…”

Section: Introductionmentioning

confidence: 99%

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Bulk Viscosity of Relativistic npeμ Matter in Neutron-Star Mergers

2022

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We discuss the bulk viscosity of hot and dense npeμ matter arising from weak-interaction direct Urca processes. We consider two regimes of interest: (a) the neutrino-transparent regime with T≤Ttr (Ttr≃5÷10 MeV is the neutrino-trapping temperature); and (b) the neutrino-trapped regime with T≥Ttr. Nuclear matter is modeled in relativistic density functional approach with density-dependent parametrization DDME2. The maximum of the bulk viscosity is achieved at temperatures T≃5÷6 MeV in the neutrino-transparent regime, then it drops rapidly at higher temperatures where neutrino-trapping occurs. As an astrophysical application, we estimate the damping timescales of density oscillations by the bulk viscosity in neutron star mergers and find that, e.g., at the oscillation frequency f=10 kHz, the damping will be very efficient at temperatures 4≤T≤7 MeV where the bulk viscosity might affect the evolution of the post-merger object.

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Section: Bulk Viscosity Of Udse Mattermentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Bulk Viscosity of Relativistic npeμ Matter in Neutron-Star Mergers

2022

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A dissipative extension to ideal hydrodynamics

Hatton,

Hawke

2024

Monthly Notices of the Royal Astronomical Society

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We present a formulation of special relativistic, dissipative hydrodynamics (SRDHD) derived from the well-established Müller-Israel-Stewart (MIS) formalism using an expansion in deviations from ideal behaviour. By re-summing the non-ideal terms, our approach extends the Euler equations of motion for an ideal fluid through a series of additional source terms that capture the effects of bulk viscosity, shear viscosity and heat flux. For efficiency these additional terms are built from purely spatial derivatives of the primitive fluid variables. The series expansion is parametrized by the dissipation strength and timescale coefficients, and is therefore rapidly convergent near the ideal limit. We show, using numerical simulations, that our model reproduces the dissipative fluid behaviour of other formulations. As our formulation is designed to avoid the numerical stiffness issues that arise in the traditional MIS formalism for fast relaxation timescales, it is roughly an order of magnitude faster than standard methods near the ideal limit.

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