Numerical Simulations     Numerical modelizing is a powerful new tool which is used in parallel and as a complement to in vitro and in vivo experimentation. Apart from setting free from usually heavy and costly experimental devices, these modelizations allow to come to a precise characterization of physical quantities of the flow, that experiments are sometimes unable to deliver. Some of them, such as the parietal frictions or even pressure are actually whether hard to quantify experimentaly or impossible without disturbing the flow. As an example, according to Ku (1997), experimental measures of the parietal frictions are only estimated and can reveal mistakes of 20 to 50%, what legitimate the importance of numerical simulations.   Over the last 5 years, the "numerical modelizing" activity has dramatically expanded inbout the laboratory. The 3D simulations, which were so far essentially processed for permanent flows, have increasingly extended to puslatory flows of physiological type. Further on, the recent integration within ESM2 of the Numerical Models Team from the Laboratory of Mechanics and Acoustics (LMA) offers possibilities of simulation in the domain of structures mechanics (endovascular materials, characterization of the comportment of arterial lining).   The numerical modelizations are realized using calculation codes (CFD 2000, N3S, Fluent) on calculators. ESM2 is equipped with several machines (Silicon Graphics : Origin 200 quadriprocessor R 10000 512 Mo, Power 256 Mo, O2 64Mo) which allow to execute calculations of industrial type. The equations of Navier-Stokes, which describe the movement of the fluid, are solved numerically, using among others, the finite elements method. This method is nowadays widely used for solving the partial differential equations. Using simple approximations of velocity and pressure variable on a discret domain, they allow to provide approached solutions from algebraic equations. The results are then post-treated with Ensight to view the velocity fields in various plans, the trajectories and the velocity isocurves, as well as the calculus of parietal shearing.