The main objective of this work is to take into account compressible fluids behaviour in those numerical models designed to represent the liquid resin flow through fibrous architectures. The aim of these models is to simulate and optimize composite materials manufacturing processes and, more specifically, the Liquid Composite Molding (LCM) method which is increasingly being adopted for the elaboration of next generation high performance composites for aerospace applications. Indeed, one of the issues related to these processes is the possible presence of voids in the finished composite part caused by air entrapment or out-gassing phenomena during the elaboration step. Thus, in order to ensure the quality of manufactured parts, it is important to understand and simulate phenomena caused by the presence of gas and so to consider its compressibility.