Gerris (software)


Gerris is computer software in the field of computational fluid dynamics. Gerris was released as free and open-source software, subject to the requirements of the GNU General Public License, version 2 or any later.

Scope

Gerris solves the Navier–Stokes equations in 2 or 3 dimensions, allowing to model industrial fluids or for instance, the mechanics of droplets, thanks to an accurate formulation of multiphase flows. Actually, the latter field of study is the reason why the software shares the same name as the insect genus.
Gerris also provides features relevant to geophysical flows:
  1. ocean tide
  2. tsunamis
  3. river flow
  4. eddies in the ocean
  5. sea state
Flow types #1 to #3 were studied using the shallow-water solver included in Gerris, case #4 brings in the primitives equations and application #5 relies on the spectral equations for generation/propagation/dissipation of swell : for this purpose Gerris makes use of the source terms from WaveWatchIII.
Lastly, one can note that the Navier–Stokes solver was also used in the ocean to study:
On the contrary Gerris does not allow the modeling of compressible fluids.

Numerical scheme

Several methods can be used to provide a numerical solution to partial differential equations:
Gerris belongs to the finite volumes family of CFD models.

Type of grid

Most models use meshes which are either structured or unstructured. Gerris is quite different on this respect: it implements a deal between structured and unstructured meshes by using a tree data structure, allowing to refine locally the description of the pressure and velocity fields. Indeed the grid evolves in the course of a given simulation owing to criteria defined by the user.

Turbulent closure

Gerris mainly aims at DNS; the range of Reynolds available to the user thus depends on the computing power they can afford. According to the Gerris FAQ the implementation of turbulence models will focus on the LES family rather than RANS approaches.

Programming language, library dependencies, included tools

Gerris is developed in C using the libraries Glib and GTS. The latter brings in facilities to perform geometric computations such as triangulation of solid surfaces and their intersection with fluid cells. Moreover Gerris is fully compliant with MPI parallelisation.
Gerris does not need a meshing tool since the local refinement of the grid is on charge of the solver itself. As far as solid surfaces are concerned, several input formats are recognized:
Among the various ways to output Gerris results, let us just mention here:
CFD software, as any software, can be developed in various "realms":
As far as CFD is concerned, a thorough discussion of these software development paths can be found in the statement by Zaleski.
Gerris was distributed as free and open-source software right from the onset of the project.

Industrial fluids