Non reflecting boundary conditions on artificial frontiersof the domain are proposed for bothincompressible and compressible Navier-Stokes equations.For incompressible flows, the boundary conditions lead to a well-posedproblem, convey properly the vortices without any reflections on theartificial limits and allow to compute turbulent flows at high Reynoldsnumbers.For compressible flows, the boundary conditions convey properly thevortices without any reflections on the artificial limits and alsoavoid acoustic waves that go back into the flow and change itsbehaviour.Numerical tests illustrate the efficiency of the various boundaryconditions.
