qasMHD

Quasi all-speed magnetohydrodynamic (qasMHD) simulation code is a C++ package for solving compressible MHD equations with a finite-difference method.
The qasMHD code has the characteristics of:

• up to 4th order accuracy in space and 3rd order accuracy in time;
• shock capturing by approximate Riemann solvers, including state-of-the-art low-dissipation all-speed solvers¹²;
• preservation of the solenoidal condition of the magnetic field by a well-designed Contrained Transport method³.

The qasMHD code is unique in that it can accurately solve MHD flows in wide-ranging Mach numbers, even when the flow is almost incompressible!
The current version supports 1D-3D space in Cartesian coordinates and hybrid MPI/OpenMP parallel computation.

System requirements

Following packages are required to be installed on the system:

• Git to install and update the qasMHD code;
• C++ compiler (GNU, Intel);
• MPI library (MPICH, OpenMPI) to use the MPI parallel code;
• Make
• Python 3.X with NumPy and matplotlib for data read and visualization (can be downloaded from Anaconda);
• (Optional) Mayavi in Python for 3D data visualization (can be installed by >pip install mayavi).

The code is tested on Linux OSs (Ubuntu, Linux Mint, CentOS, including Windows Subsystem for Linux).
Above packages (excluding Intel compiler) can be installed by apt or yum commands.

Installation

1. Download the qasMHD code from GitHub by >git clone https://github.com/minoshim/qasMHD.
2. Move to the main directory qasMHD/.
3. Check Makefile.inc and edit environment variables CC, CFLAGS, and MPICC to meet users environment.
4. Execute >make clean and >make commands to remake libraries.

Since the code is updated without notice, users may need to update the code by >git pull origin main.

Composition

• 1D/ contains serial codes for one-dimensional problems.
• 2D/ contains serial and MPI parallel codes for two-dimensional problems.
• 3D/ contains MPI parallel codes for three-dimensional problems.
• common/ contains central functions for the simulation.
• license/ contains license documents.
• mpi/ contains functions for MPI parallelization.
• Makefile to make libraries.
• Makefile.inc to define environment variables.
• README.md is this file.
• libmympi.a is the library generated from mpi/.
• libqasmhd.a is the library generated from common/.

common/mhd_class.hpp and mpi/mympi_class.hpp define the base class of the MHD simulation and MPI parallelization.
Member variables defined in common/mhd_class.hpp are:

  double gam=5.0/3.0;           // Specific heat ratio
  double *x,*y,*z;              // Spatial coordinate
  double *ro,*mx,*my,*mz,*en;   // Density, momentum, and total energy
  double *bx,*by,*bz;           // Magnetic field @ cell edge
  double *vx,*vy,*vz,*pr;       // Velocity and pressure
  double *cx,*cy,*cz;           // Magnetic field @ cell center
  double *nu,*eta;              // Kinematic viscosity and resistivity
  double *phi_g;                // Gravitational potential

and defined in mpi/mympi_class.hpp are:

  int mpi_num=1;                // Number of MPI processes
  int mpi_rank=0;               // MPI rank

For information about 1D/, 2D/, and 3D/ problems, see README in each directory.

Footnotes

1. Minoshima T., Kitamura K., and Miyoshi T. 2020, ApJS ↩

2. Minoshima T. and Miyoshi T. 2021, JCP ↩

3. Minoshima T., Miyoshi T., and Matsumoto Y. 2019, ApJS ↩