The effects of sprue base size and design on flow pattern during aluminum gravity casting have been investigated by employing different sprue base sizes and using computational fluid dynamics. Calculations were carried out using SUTCAST simulation software based on solving Navier–Stokes equation and tracing the free surface using SOLA-volume of fluid algorithm. Flow pattern was analyzed with focus on streamlines and velocity distribution in sprue base, runner and ingate. Increasing well size produced a vortex flow at the bottom of sprue base, which increased the surface velocity of liquid metal in runner. Using a rather big sprue well could eliminate vena contracta but ingate velocity was observed to be independent of well size. It is assumed that ingate velocity may be more influenced by other casting considerations. Using a curved sprue base could remove vortex flow at the bottom of sprue while keeping a nearly full contact between liquid metal and runner wall.