Air-caps or tank vent check valves are employed in ships to allow tanks to breath during filling, draining and volume variations caused by thermal changes. A numerical study of flow in such a tank venting air-cap is performed to investigate turbulent flow and pressure drop characteristics. The method is based on the fully conserved control-volume representation of fully elliptic Navier-Stokes equations. The computational grid is established by employing the non-orthogonal body-fitted coordinate system and associating them with the multi-block to handle the complex geometry. Turbulence is simulated via two equation (k-epsilon) model. The study comprises computed velocity, the kinetic energy of turbulence and pressure drop distributions for three different sizes of air-caps. For each of these cases, the Reynolds number of the air-cap was varied from about 10(4) to 4.0 X 10(6).