nstokes

Nstokes is a finite element solver for Stokes and Navier-Stokes incompressible flow problems in two and three dimensions.

Installation

1. you will need to install the ISCD Commons Library on your system. Please refer to the instructions provided on the ISCD Commons Library page in order to install this library.

2. download the zip archive of NavierStokes or clone this repository:

   git clone https://github.com/ISCDtoolbox/NavierStokes.git

   navigate to the downloaded directory:

   cd NavierStokes

   then create build directory and compile the project using cmake

   mkdir build
   cd build
   cmake ..
   make
   make install
   

Usage

After compiling nstokes as described above, you should have an executable file in your $HOME/bin directory. If your PATH variable is correctly set to this directory, nstokes can be called with the following syntax:

usage: nstokes [+/-v | -h | -N] [-dt step] [-mt val] [-nt n] [-n nit] [-r res] [-t typ] [-ts n] source[.mesh] [-p param[.nstokes]] [-s data[.sol]] [-o output[.sol]]

The square braces indicate optional arguments. Some commands have flags, some others do not.

The options and flags are:

  --help       show the syntax and exit.
  --version    show the version and date of release and exit.

  -N           Navier-Stokes solver (default Stokes)
  -dt step     time step (time units)
  -mt val      max time (time units)
  -nt n        number of time steps
  -n nit       number of iterations max for convergence
  -r res       value of the residual (Krylov space) for convergence
  -t typ       specify the type of FE space: 1: P1bP1(*), 2: P2P1
  -v           suppress any message (for use with function call).
  +v           increase the verbosity level for output.
  -w           save vorticity file.

  source.mesh    name of the mesh file
  param.nstokes  name of file containing fluid parameters
  data.sol       name of file containing the initial solution or boundary conditions
  output.sol     name of the output file (velocity+pressure)

A full description of all parameters and options that can be specified in the command line or in a parameter file [file.nstokes] can be found in the project wiki.

Quickstart

You can test the installation and look at examples by entering the demos directory and running the program:

cd demos/2d
nstokes cavity.mesh        # or equivalently:  nstokes cavity.mesh -p cavity.nstokes -o cavity.sol

that will produce an output that will look like:

user:~/code/NavierStokes/demos/2d$ nstokes cavity.mesh
 - NSTOKES, Release 5.2a, Jan. 29, 2016
   (C) Copyright 2006- , ICS-SU

 - LOADING DATA
    cavity.mesh: 555 vertices, 74 edges, 1034 triangles
    cavity.nstokes: 2 parameters
 - COMPLETED: 0.002s

 ** MODULE NSTOKES: 5.2a
    Matrix and right-hand side assembly
    Solving linear system:
     pressure: res=6.862905e-07, nit=36
     velocity: res=7.920541e-07, nit=26
 ** COMPLETED: 0.120s

 - WRITING DATA
    cavity.solb: 555 data vectors
 - COMPLETED: 0.008s

 ** Cumulative time: 0.130s.

Authors & contributors

• nstokes has been initiated by Thi Thu Cuc Bui, Dena Kazerani, Thi Thanh Mai Ta and Pascal Frey (Université Pierre et Marie Curie).
• Contributors to this project are warmly welcomed.

License

nstokes is given under the [terms of the GNU Lesser General Public License] (LICENSE.md).