FVENS

This is a cell-centered finite volume solver for the two-dimensional compressible Euler and Navier-Stokes equations. Unstructured grids having both triangles and quadrangles are supported. It includes gradient computation using either Green-Gauss or weighted least-squares methods. Linear, MUSCL and limited linear reconstructions are availble. The Van Albada limiter is used for MUSCL reconstruction while the WENO (weighted essentially non-oscillatory), Barth-Jespersen or Venkatakrishnan limiters can be used for limited linear reconstruction. A number of numerical inviscid fluxes are available - local Lax-Friedrichs (Rusanov), Van Leer flux vector splitting, AUSM, HLL (Harten - Lax - Van Leer), HLLC and Roe-Pike. Modified average gradients are used for viscous fluxes. Only steady-state problems are currently supported; both explicit and implicit pseudo-time stepping are available.

If you wish to contribute, please read the guidelines.

Features

• Almost everything implemented here is parallelized with OpenMP
• Supports 2D hybrid grids containing both triangles and quadrangles
• Several different inviscid numerical flux options available
• Two different gradient computation schemes
• Several reconstruction schemes using different limiters
• A matrix-free implicit solver implementation is available; however, it uses an approximate stored Jacobian for preconditioning
• Consideration for robustness of the non-linear solver through the use of CFL ramping and automatic underrelaxation

Limitations

• MPI support is still under development
• Two spatial dimensions only
• Not many types of boundary conditions are currently implemented - only the simplest or most common ones

Building

The following libraries and programs are required:

• Boost, present in the default package repositories of all GNU/Linux distributions
• The Eigen matrix library (version 3.3.5 or newer) - needs a variable called EIGEN3_ROOT to be set to the top-level Eigen directory
• PETSc version 3.8 or newer for sparse linear solvers; needs PETSC_DIR and PETSC_ARCH set, unless PETSc has been installed in standard system locations.
• Gmsh SDK 3.0 or later is required. It is available in most GNU/Linux distributions' official repositories. If it is not present in a standard directory and has not been added to the PATH variable, one can pass -DCMAKE_PREFIX_PATH=/path/to/top-level/gmsh-dir in the cmake command line (see below).
• Scotch 6.0 and above. Needs the variable SCOTCH_DIR to be set. The serial version is enough, PTScotch is not used (yet).
• Optionally, BLASTed sparse linear algebra library - needs an environment variable called BLASTED_DIR to be set to the top level BLASTed source directory and BLASTED_BIN_DIR to be set to the BLASTed build directory. -DWITH_BLASTED=1 needs to be passed to CMake.

The variables needed can either be passed as arguments to CMake during configuration (see below) or set as environment variables. OpenMP will be used if available (default builds of GCC on most GNU/Linux distributions have this, for instance).

To build go to the FVENS root directory and issue

	mkdir build && cd build
	cmake .. 

and for a release build

	cmake .. -DCMAKE_BUILD_TYPE=Release

-DNOOMP=1 should be appended if OpenMP is not available. -DAVX=1 etc. can be passed if your CPU supports the corresponding vector instructions. See the header of the top-level CMakeLists.txt for a list of all build options. Finally,

	make -j<N>

where '<N>' should be replaced by the number of threads to use for building. The build is known to work with recent versions of GCC C++ (5.4 and above) and Intel C++ (2017 and 2018) compilers on GNU/Linux systems.

To run the tests, run make test or ctest in the build directory.

To build the Doxygen documentation, type the following command in the doc/ directory:

	doxygen fvens_doxygen.cfg

This requires you to have Doxygen installed. It will generate HTML documentation, which can be accessed through doc/html/index.htm.

Running the code

Please refer to the user manual.

Browsing the code

A tags file is built when the code is built (if ctags is available), which makes navigation convenient. Using tags in Vim or Spacemacs is easy.

Known issues

Please see the issues page.

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Copyright (C) 2016 - 2019, Aditya Kashi. See LICENSE.md for terms of redistribution with/without modification and those of linking.

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.