__ ____ _____ ____ ___ / /__ / __ \/ ___/ / __ \ / _ \ / //_// /_/ /\__ \ / / / // __// ,< / _, _/___/ / /_/ /_/ \___//_/|_|/_/ |_|/____/ COPYRIGHT (c) 2019-2023 UCHICAGO ARGONNE, LLC

nekRS is a fast and scaleable computational fluid dynamics (CFD) solver targeting HPC applications. The code started as an early fork of libParanumal in 2019.

Capabilities:

• Incompressible and low Mach-number Navier-Stokes + scalar transport
• High-order curvilinear conformal spectral elements in space
• Variable time step 2nd/3rd order semi-implicit time integration
• MPI + OCCA (backends: CUDA, HIP, OPENCL, SERIAL/C++)
• LES and RANS turbulence models
• Arbitrary-Lagrangian-Eulerian moving mesh
• Lagrangian phase model
• Overlapping overset grids
• Conjugate fluid-solid heat transfer
• Various boundary conditions
• VisIt & Paraview support for data analysis and visualization
• Legacy interface to Nek5000

Build Instructions

Requirements: * Linux, Mac OS X (Microsoft WSL and Windows is not supported) * C++17/C99 compatible compiler * GNU/Intel/NVHPC Fortran compiler * MPI-3.1 or later * CMake version 3.18 or later

Download the latest release available under

sh https://github.com/Nek5000/nekRS/archive/refs/tags/v23.0.tar.gz

or clone our GitHub repository:

sh https://github.com/Nek5000/nekRS.git The master branch always points to the latest stable release while next provides an early preview of the next upcoming release (do not use in a production environment).

To build and install the code run:

sh CC=mpicc CXX=mpic++ FC=mpif77 ./nrsconfig [-DCMAKE_INSTALL_PREFIX=$HOME/.local/nekrs] Build settings can be customized through CMake options passed to nrsconfig. Please remove the previous build and installation directory in case of an update.

Setting the Enviroment

Assuming you run bash and your install directory is $HOME/.local/nekrs, add the following line to your $HOME/.bash_profile:

sh export NEKRS_HOME=$HOME/.local/nekrs export PATH=$NEKRS_HOME/bin:$PATH then type source $HOME/.bash_profile in the current terminal window.

Run the Code

We try hard not to break userland but the code is evolving quickly so things might change from one version to another without being backward compatible. Please consult RELEASE.md before using the code.

sh cd $NEKRS_HOME/examples/turbPipePeriodic mpirun -np 2 nekrs --setup turbPipe.par For convenience we provide various launch scripts in the bin directory.

Documentation

For documentation, see our readthedocs page. For now it's just a dummy. We hope to improve it soon.

Discussion Group

Please visit GitHub Discussions. Here we help, find solutions, share ideas, and follow discussions.

Contributing

Our project is hosted on GitHub. To learn how to contribute, see CONTRIBUTING.md.

Reporting Bugs

All bugs are reported and tracked through Issues. If you are having trouble installing the code or getting your case to run properly, you should first vist our discussion group.

License

nekRS is released under the BSD 3-clause license (see LICENSE file). All new contributions must be made under the BSD 3-clause license.

Citing nekRS

NekRS, a GPU-Accelerated Spectral Element Navier-Stokes Solver

Acknowledgment

This research was supported by the Exascale Computing Project (17-SC-20-SC), a joint project of the U.S. Department of Energy's Office of Science and National Nuclear Security Administration, responsible for delivering a capable exascale ecosystem, including software, applications, and hardware technology, to support the nation's exascale computing imperative.