TELEMAC  In computational fluid dynamics, TELEMAC is short for the open TELEMAC-MASCARET system, or a suite of finite element computer program owned by the Laboratoire National d'Hydraulique et Environnement (LNHE), part of the R&D group of Électricité de France. After many years of commercial distribution, a Consortium (the TELEMAC-MASCARET Consortium) was officially created in January 2010 to organize the open source distribution of the open TELEMAC-MASCARET system now available under GPLv3. It 2D hydrodynamics module, TELEMAC-2D, solves the so-called shallow water equations, also known as the Saint Venant equations. TELEMAC-2D solves the Saint-Venant equations using the finite-element or finite-volume method and a computation mesh of triangular elements. It can perform simulations in transient and permanent conditions. TELEMAC-2D can take into account the following phenomena: TELEMAC-2D is used in many fields of application. In the maritime field, particular mention may be made of harbour structure design, studies of the effect of building submersible breakwaters or dredging works, the impact of discharges from a sea outfall, study of thermal plumes; and, with regard to rivers, the impact of various types of construction (bridges, sills, groynes), dam breaks, flood studies, transport of dissipating or non-dissipating tracers. TELEMAC-2D can also be used for a number of special applications, such as industrial reservoir failures, avalanches falling into reservoirs, etc. It 3D hydrodynamics module, TELEMAC-3D, uses the same horizontally unstructured mesh as TELEMAC-2D but solves the Navier-Stokes equations, whether in hydrostatic or non-hydrostatic mode so allowing shorter waves than those in a shallow water context (where wavelengths are required to be at least twenty times the water depth). The wave formulation for the updating of the free surface is used for efficiency. The 3D mesh is developed as a series of meshed surfaces between the bed and the free surface. Flexibility in the placement of these planes permits the use of a sigma grid (each plane at a given proportion of the spacing between bed and surface) or a number of other strategies for intermediate surface location. One useful example is to include some planes which are at a fixed distance below the water surface, or above the bed.