Absorbing boundary conditions for free boundaries

To ensure the exit of vortices from an open computational domain, new boundary, conditions for compressible Navier-Stokes equations, called 'absorbing conditions', are introduced. They use a layer around computational domain which eliminates nonphysical perturbations. They, are compared to three kinds of boundary conditions based on characteristic relations. Computations of two test cases show the best behaviours of the new boundary), conditions. These last ones involve a very small perturbation and can be used to solve aeroacoustic problems. (C) 2001 Academie des sciences/Editions scientifiques et medicales Elsevier SAS.