Gerris uses an "embedded boundary" technique. Grid generation reduces to the computation of the "shape" (surface and volume fractions) of Cartesian (cubic) cells cut by the solid boundaries. These "boolean operations" between solids are performed automatically using GTS (the GNU Triangulated Surface Library). The cells cut by the boundaries can then be refined automatically using the quad/octree structure of the discretisation.
Mesh generation is entirely automatic and works for any input geometry. Gerris uses a quadtree (octree in 3D) finite volume discretisation. It cannot handle unstructured meshes.
A brief summary of its main features:
- Solves the time-dependent incompressible variable-density Euler, Stokes or Navier-Stokes equations.
- Solves the linear and non-linear shallow-water equations.
- Adaptive mesh refinement: the resolution is adapted dynamically to the features of the flow.
- Entirely automatic mesh generation in complex geometries.
- Second-order in space and time.
- Unlimited number of advected/diffused passive tracers.
- Flexible specification of additional source terms.
- Portable parallel support using the MPI library, dynamic load-balancing, parallel offline visualisation.
- Volume of Fluid advection scheme for interfacial flows.
- Accurate surface tension model.
- Multiphase electrohydrodynamics.