EXACT AND APPROXIMATE BOUNDARY-CONDITIONS AT ARTIFICIAL BOUNDARIES

The use of transformation methods for the derivation of boundary conditions at artificial boundaries had been initiated by Engquist and Majda [4, 5]. They considered the scalar wave equation and strictly hyperbolic systems. This has been extended by Gustafsson [11] to inhomogeneous conditions, by Hagstrom [15] to parabolic and Halpern et al. [17, 20] to incompletely parabolic systems. Here a systematic method is developed which unifies these approaches. Additionally, inhomogeneities with non-compact support are taken into account. Exact and first-order approximate boundary conditions for the compressible Navier-Stokes equations are presented.