The fundamentals of flow in the liquid composite moulding (LCM) processes are reviewed with an emphasis on multiphase flow effects considering the dual-scale thin porous media constituted by the textiles, and the dynamic wetting effects observed with viscous fluids. The main physical phenomena governing multiphase fluid flow in porous media are presented, using a continuum mechanics approach. Strategies towards solving these equations are then reviewed. Two main approaches are currently developed in the LCM literature. One is a direct solution of the multiphase flow equations, which requires dual knowledge of how permeability varies with saturation, and how saturation varies with pressure. The other is an indirect method based on solution of saturated flow with the introduction of sink terms, representing the dual scale of the fibrous reinforcements, which requires knowledge of the flow kinetics within the tows. Even though a complete and accurate tool to simulate multiphase LCM flow is still far from being available, several recent results have contributed to improving our physical understanding of LCM processes leading to process kinetics optimization and possibly porosity reduction in the final part.