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We introduce a new computational method for embedding Lagrangian sink particles into an Eulerian calculation. Simulations of gravitational collapse or accretion generally produce regions whose density greatly exceeds the mean density in the…

Astrophysics · Physics 2009-11-10 Mark R. Krumholz , Christopher F. McKee , Richard I. Klein

In this work, a second-order approximation of the fractional substantial derivative is presented by considering a modified shifted substantial Gr\"{u}nwald formula and its asymptotic expansion. Moreover, the proposed approximation is…

Numerical Analysis · Mathematics 2016-07-26 Zhaopeng Hao , Wanrong Cao , Guang Lin

Despite the many advances in the use of weakly-compressible smoothed particle hydrodynamics (SPH) for the simulation of incompressible fluid flow, it is still challenging to obtain second-order convergence even for simple periodic domains.…

Numerical Analysis · Mathematics 2022-09-07 Pawan Negi , Prabhu Ramachandran

We have generalised the exact solution of the Riemann problem in special relativistic hydrodynamics for arbitrary tangential flow velocities. The solution is obtained by solving the jump conditions across shocks plus an ordinary…

Astrophysics · Physics 2017-05-17 Jose A. Pons , Jose Ma. Marti , Ewald Mueller

We propose a novel Skew Gradient Embedding (SGE) framework for systematically reformulating thermodynamically consistent partial differential equation (PDE) models-capturing both reversible and irreversible processes-as generalized gradient…

Numerical Analysis · Mathematics 2025-09-24 Xuelong Gu , Qi Wang

We compare here several modern versions of SPH with a particular focus on the impact of gradient accuracy. We examine specifically an approximation to the "linearly exact" gradients (aLE) with standard SPH kernel gradients and with linearly…

Instrumentation and Methods for Astrophysics · Physics 2026-02-10 S. Rosswog

Stochastic differential equations (SDEs) on Riemannian manifolds have numerous applications in system identification and control. However, geometry-preserving numerical methods for simulating Riemannian SDEs remain relatively…

Numerical Analysis · Mathematics 2025-04-18 Xi Wang , Victor Solo

We introduce a generalization of Glimm's random choice method, which provides us with an approximation of entropy solutions to quasilinear hyperbolic system of balance laws. The flux-function and the source term of the equations may depend…

Analysis of PDEs · Mathematics 2007-05-23 John M. Hong , Philippe G. LeFloch

We show in this paper that third- and fourth-order low storage Runge-Kutta algorithms can be built specifically for quadratic nonlinear operators, at the expense of roughly doubling the time needed for evaluating the temporal derivatives.…

Fluid Dynamics · Physics 2008-08-14 Marc E. Brachet , Pablo D. Mininni , Duane L. Rosenberg , Annick Pouquet

In this paper, the nonlocal reverse space-time derivative nonlinear Schr\"odinger equation under nonzero boundary conditions is investigated using the Riemann-Hilbert (RH) approach. The direct scattering problem focuses on the analyticity,…

Exactly Solvable and Integrable Systems · Physics 2024-06-21 Xin-Yu Liu , Rui Guo

We present a new algorithm for solving ideal relativistic hydrodynamics based on Godunov method with an exact solution of Riemann problem for an arbitrary equation of state. Standard numerical tests are executed, such as the sound wave…

Nuclear Theory · Physics 2015-06-11 Zuzana Feckova , Boris Tomasik

In this paper, we describe a new hydrodynamics code for 1D and 2D astrophysical simulations, BETHE-hydro, that uses time-dependent, arbitrary, unstructured grids. The core of the hydrodynamics algorithm is an arbitrary Lagrangian-Eulerian…

Astrophysics · Physics 2009-11-13 Jeremiah W. Murphy , Adam Burrows

A fully implicit finite difference scheme has been developed to solve the hydrodynamic equations coupled with radiation transport. Solution of the time dependent radiation transport equation is obtained using the discrete ordinates method…

Fluid Dynamics · Physics 2008-07-14 Karabi Ghosh , S. V. G. Menon

We present an analytic solution of the Riemann problem for the equations of relativistic hydrodynamics with the ultra-relativistic equation of state and non-zero tangential velocities. A 3-dimensional numerical code solving such equations…

Mathematical Physics · Physics 2010-07-12 Patryk Mach

We present the foundations of a new solution technique for the characteristic initial value problem (IVP) of colliding plane gravitational waves. It has extensive similarities to the approach of Alekseev and Griffiths in 2001, but we use an…

General Relativity and Quantum Cosmology · Physics 2018-01-23 Stefan Palenta , Reinhard Meinel

Flash evaporation, a liquid-to-gas phase transition phenomenon in real fluids, is prevalent in aerospace propulsion systems. To elucidate the physical mechanisms of such complex flows and provide theoretical benchmarks for Computational…

Fluid Dynamics · Physics 2026-01-27 Haotong Bai , Ping Yi , Yixin Yang , Guoyan Zhao , Wenjia Xie , Mingbo Sun

We propose an {\em implementable} numerical scheme for the discretization of linear-quadratic optimal control problems involving SDEs in higher dimensions with {\em control constraint}. For time discretization, we employ the implicit Euler…

Analysis of PDEs · Mathematics 2024-12-12 Abhishek Chaudhary

The paper presents the solutions for the zonal electrophoresis equations are obtained by analytical and numerical methods. The method proposed by the authors is used. This method allows to reduce the Cauchy problem for two hyperbolic…

General Physics · Physics 2015-03-06 E. V. Shiryaeva , M. Yu. Zhukov

The dynamics of self-gravitating fluid bodies is described by the Euler-Einstein system of partial differential equations. The break-down of well-posedness on the fluid-vacuum interface remains a challenging open problem, which is…

General Relativity and Quantum Cosmology · Physics 2020-07-17 John Ryan Westernacher-Schneider , Charalampos Markakis , Bing Jyun Tsao

First-order hydrostatic reconstruction (HR) schemes for shallow water equations are highly diffusive whereas high-order schemes can produce entropy-violating solutions. Our goal is to develop a flux correction with maximum antidiffusive…

Numerical Analysis · Mathematics 2024-02-23 Sergii Kivva