The most limiting aspect in liquid composite molding processes is the porosity issue. A successful manufacturing design depends mainly on the accurate prediction of the dynamics of air bubbles while processing composite structures. Especially, while simulating with a constant injection flow rate, where the part is supposed to exhibit a uniform porosity distribution according to the capillary number theory as proposed in the literature, it is not true in real practice. With this motivation, we present here a new approach, based on intra and intertow flows competition, to quantify the porosity of resin transfer molded composite parts. Combining the numerical modeling of the resin transfer molding (RTM) process based on the control volume finite element and volume of fluid methods on one hand, and the pore doublet model (PDM) on the other hand, air bubble contents at dual scale of pores are modeled in the case of constant pressure and constant injection flow rate. The results of the developed modeling permit a detailed spatiotemporal description of the created compressed and transported micro and macro air bubbles, besides fibrous fabric saturation. Consequently, taking into account the compression and transport phenomena, the porosity distribution is no longer uniform in the part, but higher in the downstream than in the upstream. Furthermore, the void transport phenomenon is also considered using the PDM concept. To validate the proposed approach, the numerical and experimental data are compared. © 2019, Springer-Verlag London Ltd., part of Springer Nature.