The French Atomic Energy Commission has developed the FAUST (Focusing Adaptive UltraSonic Tomography) system, based on optimized phased array transducers connected to a multi-channel acquisition system supplying delay and amplitude laws forming the ultrasonic beam. The model Champ-Sons supplies the system with focusing parameters. This model is based on the Rayleigh integral propagation model, modified to take account of interface with complex geometry. It allows both calculation of delay laws and related ultrasonic field in solids. Some simulations of inspection are presented showing the capability of the association between phased array techniques and modeling to enhance the inspection of a specimen with a varying profile.