<p>This study investigates the internal flow regime of ventilated supercavities featuring two closure types: twin-vortex and re-entrant jet. A solver based on the inhomogeneous multiphase model was developed to predict the supercavitation flow. The effectiveness of the numerical model was thoroughly validated against experimental data. Furthermore, a comprehensive analysis was conducted to elucidate the internal flow structure and examine the transient flow behavior associated with both twin-vortex and re-entrant jet supercavities. The results indicate that a flow structure characterized by gas recirculation, which includes both the reverse flow region and downstream flow region, is present within both types of supercavities. In twin-vortex supercavities, the interaction between the two opposing flow domains leads to significant transient characteristics and substantial deformation of the interface. An increase in the ventilation rate diminishes the fluctuation characteristics of the supercavity geometry; however, the internal gas flow remains intense and complex. In the case of re-entrant jet supercavities, the vertical extent of the downstream flow region is smaller compared to that of the reverse flow region. Additionally, the ratio of the vertical extent of the downstream flow region to the cross-sectional dimension of the supercavity is contingent upon the geometry of the supercavitating vehicle.</p>