Relativistic hydrodynamic flows using spatial and temporal adaptive structured mesh refinement

Astrophysical relativistic flow problems require high-resolution three-dimensional (3D) numerical simulations. In this paper, we describe a new parallel 3D code for simulations of special relativistic hydrodynamics (SRHD) using both spatially and temporally structured adaptive mesh refinement (AMR). We used the method of lines to discretize the SRHD equations spatially and a total variation diminishing (TVD) Runge-Kutta scheme for time integration. For spatial reconstruction, we have implemented piecewise linear method (PLM), piecewise parabolic method (PPM), third-order convex essentially nonoscillatory (CENO) and third- and fifth-order weighted essentially nonoscillatory (WENO) schemes. Flux is computed using either direct flux reconstruction or approximate Riemann solvers including HLL, modified Marquina flux, local Lax-Friedrichs flux formulas, and HLLC. The AMR part of the code is built on top of the cosmological Eulerian AMR code enzo. We discuss the coupling of the AMR framework with the relativistic solvers. Via various test problems, we emphasize the importance of resolution studies in relativistic flow simulations because extremely high resolution is required especially when shear flows are present in the problem. We also present the results of two 3D simulations of astrophysical jets: AGN jets and GRB jets. Resolution study of those two cases further highlights the need of high resolutions to calculate accurately relativistic flow problems.