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A neutron star in a compact binary is expected to be well-approximated by a barotropic flow during the inspiral phase. During the merger phase, where tidal disruption and shock-heating occur, a baroclinic description is needed instead. In…

High Energy Astrophysical Phenomena · Physics 2020-06-19 John Ryan Westernacher-Schneider

One of the main challenges in the numerical modeling of binary neutron-star (BNS) mergers is long-term simulations of the post-merger remnant over timescales of the order of seconds. When this modeling includes all the aspects of complex…

General Relativity and Quantum Cosmology · Physics 2024-04-11 Harry Ho-Yin Ng , Jin-Liang Jiang , Carlo Musolino , Christian Ecker , Samuel D. Tootle , Luciano Rezzolla

We implement general relativistic hydrodynamics in the moving-mesh code AREPO. We also couple a solver for the Einstein field equations employing the conformal flatness approximation. The implementation is validated by evolving isolated…

High Energy Astrophysical Phenomena · Physics 2024-01-10 Georgios Lioutas , Andreas Bauswein , Theodoros Soultanis , Rüdiger Pakmor , Volker Springel , Friedrich K. Röpke

We present numerical results on two- (2D) and three-dimensional (3D) hydrodynamic core-collapse simulations of an 11.2$M_\odot$ star. By changing numerical resolutions and seed perturbations systematically, we study how the postbounce…

Solar and Stellar Astrophysics · Physics 2015-06-17 Tomoya Takiwaki , Kei Kotake , Yudai Suwa

The early post-merger phase of a binary neutron-star coalescence is shaped by characteristic rotational velocities as well as violent density oscillations and offers the possibility to constrain the properties of neutron star matter by…

General Relativity and Quantum Cosmology · Physics 2025-03-10 Michail Chabanov , Luciano Rezzolla

Hydrodynamical interaction in circumbinary discs (CBDs) plays a crucial role in various astrophysical systems, ranging from young stellar binaries to supermassive black hole binaries in galactic centers. Most previous simulations of…

High Energy Astrophysical Phenomena · Physics 2023-09-20 Hai-Yang Wang , Xue-Ning Bai , Dong Lai , Douglas N. C. Lin

Direct numerical simulations (DNS) are accurate but computationally expensive for predicting materials evolution across timescales, due to the complexity of the underlying evolution equations, the nature of multiscale spatio-temporal…

Machine Learning · Computer Science 2023-12-12 Vivek Oommen , Khemraj Shukla , Saaketh Desai , Remi Dingreville , George Em Karniadakis

A new class of Hermite methods for solving nonlinear conservation laws is presented. While preserving the high order spatial accuracy for smooth solutions in the existing Hermite methods, the new methods come with better stability…

Numerical Analysis · Mathematics 2017-03-21 Adeline Kornelus , Daniel Appelö

In this work, we design an entropy stable, finite volume approximation for the ideal magnetohydrodynamics (MHD) equations. The method is novel as we design an affordable analytical expression of the numerical interface flux function that…

Numerical Analysis · Mathematics 2015-10-01 Andrew R. Winters , Gregor J. Gassner

This paper describes a numerical scheme for multi-fluid hydrodynamics in the limit of small mass densities of the charged particles. The inertia of the charged particles can then be neglected, which makes it possible to write an evolution…

Astrophysics · Physics 2009-11-10 S. A. E. G. Falle

The merger of binary neutron stars, or of a neutron star and a stellar-mass black hole, can result in the formation of a massive rotating torus around a spinning black hole. In addition to providing collimating media for gamma-ray burst…

High Energy Astrophysical Phenomena · Physics 2017-12-13 Daniel M. Siegel , Brian D. Metzger

We consider coupled models for particulate flows, where the disperse phase is made of particles with distinct sizes. We are thus led to a system coupling the incompressible Navier-Stokes equations to the multi-component Vlasov-Fokker-Planck…

Numerical Analysis · Mathematics 2022-12-20 Shi Jin , Yiwen Lin

We employ an approximate treatment of dissipative hydrodynamics in three dimensions to study the coalescence of binary neutron stars driven by the emission of gravitational waves. The stars are modeled as compressible ellipsoids obeying a…

Astrophysics · Physics 2009-10-22 Dong Lai , Stu Shapiro

Highly eccentric binary neutron star mergers exhibit unique dynamical and observational signatures compared to quasi-circular ones in terms of their gravitational wave signal and the ejection of matter, leading to different electromagnetic…

General Relativity and Quantum Cosmology · Physics 2025-04-15 Anna Neuweiler , Tim Dietrich , Bernd Brügmann

In the present article we describe a few simple and efficient finite volume type schemes on moving grids in one spatial dimension combined with appropriate predictor-corrector method to achieve higher resolution. The underlying finite…

Numerical Analysis · Mathematics 2020-05-26 Gayaz Khakimzyanov , Denys Dutykh , Dimitrios Mitsotakis , Nina Shokina

Viscosity and magnetic fields drive differentially rotating stars toward uniform rotation, which has important consequences in many astrophysical contexts. For example, merging binary neutron stars can form a "hypermassive" remnant, i.e. a…

Astrophysics · Physics 2009-11-10 Matthew D. Duez , Yuk Tung Liu , Stuart L. Shapiro , Branson C. Stephens

In the proceedings of this, and of several recent close binary conferences, there have been several contributions describing smoothed particle hydrodynamics simulations of accretion disks. It is apposite therefore to review the numerical…

Astrophysics · Physics 2007-05-23 J. R. Murray , M. R. Truss , S. B. Foulkes , C. A. Haswell , K. Manson

We review and compare numerical methods that simultaneously control temperature while preserving the momentum, a family of particle simulation methods commonly used for the modelling of complex fluids and polymers. The class of methods…

Computational Physics · Physics 2020-02-14 Benedict Leimkuhler , Xiaocheng Shang

The macroscale structure and microscale fluctuation statistics of late-time asymptotic steady state flows in cylindrical geometries is studied using the methods of equilibrium statistical mechanics. The axisymmetric assumption permits an…

Fluid Dynamics · Physics 2019-06-05 Peter B. Weichman

We discuss (3+1) dimensional general relativistic hydrodynamic simulations of close neutron star binary systems. The relativistic field equations are solved at each time slice with a spatial 3-metric chosen to be conformally flat. Against…

General Relativity and Quantum Cosmology · Physics 2007-05-23 G. J. Mathews , P. Marronetti , J. R. Wilson