Finite-element-based Navier-Stokes solvers

This project provides efficient solvers for the Navier-Stokes equations based on high-order discontinuous Galerkin finite element methods. By the use of efficient solution algorithms as well as solvers and preconditioners based on the matrix-free paradigm, this project aims at offering next generation's fluid solvers exploiting modern computer hardware and being prepared for the massively parallel era.

Installation of software

As a prerequisite to get access to the code, a new user has to login at https://gitlab.lrz.de/ with the TUMOnline account ab12xyz so that the user can be added to the project.

Structure of folders

Go to your working_directory

cd /working_directory/

N.B.: For students at LNM, the scratch-directory has to be used (as opposed to the home directory) as a folder for the subsequent installations

cd /scratch/students_name/

This directory is called working_directory in the following.

For other users, the working directory might for example be

cd /home/username/

Add the following variable to your environment (in case you want to make the setting permanent, e.g. by inserting the following line into your bashrc-file)

export WORKING_DIRECTORY=/working_directory

We now create a folder called workspace in the working_directory/ where we will later install the navierstokes code

mkdir workspace

Since we also have to install other software packages apart from the navierstokes code, we create another folder called sw (software) for third party software packages

mkdir sw

navierstokes code (part 1)

Go to the workspace-folder in your working directory

cd /working_directory/workspace/

Fork navierstokes project

Fork from the supervisor's navierstokes project [email protected]:supervisor_id/navierstokes.git, e.g.,

[email protected]:ga34jem/navierstokes.git (Niklas) or [email protected]:ne96pad/navierstokes.git (Martin).

This has to be done on website https://gitlab.lrz.de/ (open the supervisor's navierstokes project and press the Fork button). As a result, a navierstokes project with the student's ID ab12xyz is created.

git clone https://gitlab.lrz.de/ab12xyz/navierstokes.git
cd navierstokes/
git remote add supervisor https://gitlab.lrz.de/supervisor_id/navierstokes.git

Interlude - install other software packages

Trilinos code (optional)

For some functionalities in the navierstokes code (e.g., algebraic multigrid solver), trilinos is required. The default setting is to not install trilinos and installing this package is optional.

If you want to use trilinos, go to the sw-folder in your working directory

cd /working_directory/sw/

Download trilinos and run the following commands

wget https://github.com/trilinos/Trilinos/archive/trilinos-release-12-12-1.tar.gz
tar xf trilinos-release-12-12-1.tar.gz 
cd Trilinos-trilinos-release-12-12-1/

mkdir build
cd build/

Copy the script config_trilinos.sh from the folder navierstokes/scripts/ to the current folder, e.g.,

cp /working_directory/workspace/navierstokes/scripts/config_trilinos.sh .

N.B.: To get these scripts, you first have to perform the first steps of the navierstokes installation described above, i.e., you have to fork and clone the navierstokes project.

Next, adapt the directory settings at the top of the script and run the script

bash ./config_trilinos.sh

For clusters @LNM: Load modules

module load mpi/openmpi-4.0.1
module load gcc/8

and adapt MPIDIR in config_trilinos.sh. Find out the path by

module show mpi/openmpi-4.0.1

Next, build the code

make -j2
make install

Metis code (optional)

For some functionalities in the navierstokes code (e.g., graph partitioning), metis is required. The default setting is to not install metis and installing this package is optional.

If you want to use metis, go to the sw-folder in your working directory

cd /working_directory/sw/

Download metis and run the following commands

git clone https://github.com/scibuilder/metis.git
cd metis
cmake .
make

deal.II code

The navierstokes code uses the deal.II library (https://www.dealii.org/), which is an open source finite element library based on the object-oriented C++ programming language.

Go to the sw-folder in your working directory

cd /working_directory/sw/

Clone the deal.II code from the gitlab project called matrixfree

git clone https://gitlab.lrz.de/ne96pad/matrixfree.git

Download p4est

wget http://p4est.github.io/release/p4est-2.0.tar.gz

and run the command

matrixfree/doc/external-libs/p4est-setup.sh p4est-2.0.tar.gz `pwd`

Create a folder build

mkdir build
cd build/

Copy the script config_dealii.sh from the folder navierstokes/scripts/ to the current folder, e.g.,

cp /working_directory/workspace/navierstokes/scripts/config_dealii.sh .

N.B.: To get these scripts, you first have to perform the first steps of the navierstokes installation described above, i.e., you have to fork and clone the navierstokes project.

Next, adapt the directory settings at the top of the script and switch on trilinos/metis if desired (and adjust the folder if necessary)

...
-D DEAL_II_WITH_TRILINOS:BOOL="ON" \
-D DEAL_II_WITH_METIS:BOOL="ON" \
...

Run the config-script

bash ./config_dealii.sh

Build the deal.II code

make -j2

fftw code (optional)

Install fftw (Fast Fourier transformation) for evaluation of kinetic energy spectra:

Download fftw from homepage http://www.fftw.org/download.html and copy to folder sw

cd /working_directory/sw/
wget http://fftw.org/fftw-3.3.7.tar.gz
tar -xf fftw-3.3.7.tar.gz
cd fftw-3.3.7
./configure --enable-mpi --prefix=/working_directory/sw/fftw-3.3.7-install
make
make install
cd ../fftw-3.3.7-install/lib/

Copy the script combine_fftw.sh from the folder navierstokes/scripts/ to the current folder, e.g.,

cp /working_directory/workspace/navierstokes/scripts/combine_fftw.sh .

N.B.: To get these scripts, you first have to perform the first steps of the navierstokes installation described above, i.e., you have to fork and clone the navierstokes project.

Run the script in order to combine the two libraries libfftw3.a and libfftw3_mpi.a

bash ./combine_fftw.sh

Add the following variable to your environment (in case you want to make the setting permanent, e.g. by inserting the following lines into your bashrc-file)

export FFTW_INC="$WORKING_DIRECTORY/sw/fftw-3.3.7-install/include"
export FFTW_LIB="$WORKING_DIRECTORY/sw/fftw-3.3.7-install/lib/combined"

navierstokes code continued (part 2)

Link deal.II code and build the code

cd navierstokes/

Copy the script config_navierstokes.sh from the folder navierstokes/scripts/ to the current folder, e.g.,

cp /working_directory/workspace/navierstokes/scripts/config_navierstokes.sh .

Deactivate the fftw related lines in config_navierstokes.sh if not needed, i.e., set

...
-D USE_DEAL_SPECTRUM=OFF \
...

and run the config-script

bash ./config_navierstokes.sh

In folder navierstokes, run the command

make release

and build navierstokes code

cd applications/
make -j2

You can now run your first simulations by selecting a test case in one of the my_application.cc files (e.g., incompressible_navier_stokes.cc), setting the desired parameters in the my_application_test_cases/my_test_case.h header-file, and running

mpirun -np xxx ./my_application

Switching to debug-version

To build the debug-version, run the following commands

cd ../
make debug
cd applications/
make -j2

and reactivate release-version after debugging via

cd ../
make release
cd applications/
make -j2

Working with git

Get recent updates of the supervisor's navierstokes code

git pull supervisor master

Commit changes and push:

Run clang-format for all files that have been changed, e.g.,

clang-format -i changed_file.cpp
clang-format -i new_file.h

Get an overview of what has been changed and add/commit. The following commands are used alternatingly

git status
git add changed_file.cpp new_file.h
git commit -m "a message describing what has been done/changed"

and finally push

git push

Start a merge-request on the website https://gitlab.lrz.de/:

Open your own navierstokes project, and press button Merge Requests. Select your own project as source and the supervisor's project as target.

Setup an eclipse project

Open eclipse and choose folder workspace as "workspace" in eclipse

1. File > New > Project > C/C++ > Makefile Project with Existing Code

• fill in Project Name = navierstokes
• Existing Code Location = /working_directory/workspace/navierstokes/
• disable C, enable C++
• choose Cross GCC

2. Project > Properties > C/C++ Build

• use default build command or user specified build command, e.g., make -j4
• fill in build directory (choose navierstokes/applications)

3. Project > Properties > C/C++ General > Code Analysis: disable 'syntax and semantic errors'
4. Project > Properties > C/C++ General > Formatter: lnm/styles/baci-eclipse-style
5. Project > Properties > C/C++ General > Paths and Symbols: use /working_directory/sw/matrixfree/include (for Assembly, GNU C, GNU C++)
6. Window > Preferences > General > Editors > Text Editors > Annotations > C/C++ Indexer Markers > uncheck all checkboxes > Apply > OK