N3S : A 3D Finite Element Code for Fluid Mechanics; Emphasis to Vectorization and Sparse Matrix Problems

N3S is a three-dimensional incompressible Navier-Stokes finite element code developped at EDF for the study of industrial flows*). The treatment of complex geometries, the number of nodes (up to 50000) led us to decompose the problem at different levels (geometry, algorithm and numeric). The use of the splitting up technique allows a specific and efficient treatment to be applied to each part of the Navier-Stokes equations: method of characteristics for the advection terms,conjugate gradient method for the diffusion-continuity part.