The paper describes the development of a wall model to extend the applicability of Immersed Boundary methods to high Reynolds number flows. A two-layer approach, based on a decomposition of the near-wall region, is adopted. An outer region is governed by the compressible RANS equations which are solved numerically by using a classical finite volume method. In the proximity of the wall, an inner zone is established and modelled by a simplified version of the thin-boundary-layer equations. The simulation platform is based on Cartesian meshes and an immersed boundary technique. It is able to solve the steady Euler/RANS equations in two- and three-dimensional coordinates. The robustness and the accuracy of the methodology are discussed. At present this work represents the last advance of a research activity whose final goal is a fast pre-design tool for aeronautical/industrial applications.