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Charlotte Renauld - 26/04/2016

A meeting with Gamma3

The Gamma3 project-team became part of Inria Saclay-Île-de-France Research Centre on 1st, January, 2016. It works on the robustness and speed of the algorithms used to develop numerical simulation softwares that are known and recognised all over the world. Paul-Louis George, Gamma3 team leader, enthusiastically explained to us how his team works and how it continues to validate and distribute software all over the world. 

The name Gamma is an acronym that stands for Génération Automatique de Maillages et Méthodes Avancées (automatic generation of meshes and advanced methods). Gamma3 is the successor of the Gamma team created in 1995 when it became joint with the Troyes University of Technology. Gamma "Troyes" was born of this partnership.

The team works on mesh generation, which means dividing three-dimensional objects into tetrahedra, for example. When the project started in the 1990s, Paul-Louis George, Frédéric Hecht and Eric Saltel addressed this complex topic that no-one had tackled before, and managed to write automatic mesh generating software: GHS3D.

"We were just three guys who set out to find a satisfactory solution to a real problem that had not been solved before," explains Paul-Louis George. Over the years, the team has developed other software, pushing the robustness and speed of the algorithms a little further each time.

Long-lasting software

GHS3D can model any type of object and is used by numerical simulation software: e.g. propagation of the shock wave from an explosion, air flow around an aircraft, etc. The software was created in the 1990s, it still works, and it is still being sold.

Paul-Louis George says: "That is the real difference between Gamma3 and its competitors (of which there are not many in this field): long-lasting software that has been around for more than a decade, still works, and will keep working. Our expertise is not temporary. We are in this for the long haul. "

How the team operates

Gamma3 is a close-knit team in which each member contributes to achieving a common goal. To obtain a numerical simulation and look at increasingly complicated problems, the process begins with the geometrical creation of the object. Next come the mesh generators that create the mesh of the surface and the mesh generators that create the mesh of the object's volume. To go beyond the simple creation of a mesh, the team calls on solvers to calculate, solve and qualify an equation set by a method that estimates the size and directionality of the mesh elements. This method lets you start the meshing calculation process afresh each time, with new, refined data, to obtain increasingly accurate solutions. Finally, the person who writes the display algorithms steps in so that the meshing produced can be viewed on screen.

"Our error control research work lets us minimise the number of elements in the mesh. We place the elements where they should be, with the right size and direction," says Paul-Louis George. 

Gamma3 is a robust team that continues to excel in its field, offering solutions that are unrivalled in speed and accessibility.

Thanks to the mesh generators and solvers, we have all raised our game together and discovered that we were able to go after real problems that we could not have tackled individually.

Keywords: Gamma3 Paul-Louis George Mesh Inria Saclay - Île-de-France