106 research outputs found
Relativistic Magnetohydrodynamics: Renormalized eigenvectors and full wave decomposition Riemann solver
We obtain renormalized sets of right and left eigenvectors of the flux vector
Jacobians of the relativistic MHD equations, which are regular and span a
complete basis in any physical state including degenerate ones. The
renormalization procedure relies on the characterization of the degeneracy
types in terms of the normal and tangential components of the magnetic field to
the wavefront in the fluid rest frame. Proper expressions of the renormalized
eigenvectors in conserved variables are obtained through the corresponding
matrix transformations. Our work completes previous analysis that present
different sets of right eigenvectors for non-degenerate and degenerate states,
and can be seen as a relativistic generalization of earlier work performed in
classical MHD. Based on the full wave decomposition (FWD) provided by the the
renormalized set of eigenvectors in conserved variables, we have also developed
a linearized (Roe-type) Riemann solver. Extensive testing against one- and
two-dimensional standard numerical problems allows us to conclude that our
solver is very robust. When compared with a family of simpler solvers that
avoid the knowledge of the full characteristic structure of the equations in
the computation of the numerical fluxes, our solver turns out to be less
diffusive than HLL and HLLC, and comparable in accuracy to the HLLD solver. The
amount of operations needed by the FWD solver makes it less efficient
computationally than those of the HLL family in one-dimensional problems.
However its relative efficiency increases in multidimensional simulations.Comment: 50 pages, 17 figures (2 in color). Submitted to ApJ Suppl. Se
On the application of Jacobian-free Riemann solvers for relativistic radiation magnetohydrodynamics under M1 closure
Radiative transfer plays a major role in high-energy astrophysics. In
multiple scenarios and in a broad range of energy scales, the coupling between
matter and radiation is essential to understand the interplay between theory,
observations and numerical simulations. In this paper, we present a novel
scheme for solving the equations of radiation relativistic magnetohydrodynamics
within the parallel code L\'ostrego. These equations, which are formulated
taking successive moments of the Boltzmann radiative transfer equation, are
solved under the gray-body approximation and the M1 closure using an IMEX time
integration scheme. The main novelty of our scheme is that we introduce for the
first time in the context of radiation magnetohydrodynamics a family of
Jacobian-free Riemann solvers based on internal approximations to the
Polynomial Viscosity Matrix, which were demonstrated to be robust and accurate
for non-radiative applications. The robustness and the limitations of the new
algorithms are tested by solving a collection of one-dimensional and
multi-dimensional test problems, both in the free-streaming and in the
diffusion radiation transport limits. Due to its stable performance, the
applicability of the scheme presented in this paper to real astrophysical
scenarios in high-energy astrophysics is promising. In future simulations, we
expect to be able to explore the dynamical relevance of photon-matter
interactions in the context of relativistic jets and accretion discs, from
microquasars and AGN to gamma-ray bursts.Comment: 21 pages, 13 figures. Accepted for publication in Computer Physics
Communication
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