Clinical success of extracorporeal membrane oxygenation (ECMO) depends on the proper venous cannulation. Venovenous (VV) ECMO is the preferred clinical intervention as it provides a single-site access by utilizing a VV double lumen cannula (VVDLC) with a higher level of mobilization and physical rehabilitation. Concurrent venous blood drainage and oxygenated blood infusion in the right atrium at the presence of the cannula makes the flow dynamics complex where potential mixing of venous and oxygenated blood can drastically decrease the overall performance of ECMO. There are no studies focusing on the neonatal and pediatric populations, in which the flow related effects are critical due to the small atrium size. In this study, fluid dynamics of infusion outflow jet for two commercially available neonatal VVDLC is analyzed using particle image velocimetry (PIV). Moreover, six new designs are proposed for the infusion channel geometry and compared. Important flow parameters such as flow turning angle (FTA), velocity decay, potential core, and turbulent intensity are investigated for the proposed models. The experiments showed that the outflow parameters of commercial cannulae such as FTA are strongly dependent on the operating Re number. This may result in a drastic efficiency reduction for cannula operating at off-design flow conditions. Moreover, the infusion outlet tip structure and jet internal guiding pathway (JIGP) was observed to greatly affect the outflow flow features. This is of paramount importance since the anatomical positioning of the cannula and the infusion outlet is strongly dependent on the outflow properties such as FTA.