Absrtact A shaft spillway is an uncontrolled spillway in which the water enters over a weir and drops through a vertical or sloping shaft into a conduit discharging into the downstream channel. These are circling spillways used generally for draining unexpected floods on earth- and concrete dams. The drop-inlet and the morning-glory are the two most common shaft spillways used for these purposes. The morning glory spillway is a special case of the circular sharp crested weir in which the shape of the weir crest and the upper portion of the shaft are designed to follow the trajectory of the lower nape. Morning glory spillway used while the other types of spillways are useless. However, the limitations on discharge coefficient of this spillway, results in increasing the water head in the reservoir and subsequently, increase the risk of damage. Consequent to the onset of submergence, the head-loss increases, swirling flow generates, vortices intensify and the performance of spillway on evacuating flow decreases severely. Intake vortices are the result of angular momentum conservation at the flow constriction, where angular velocity increases with a decrease in the cross sectional area. The strong vortices over the inlet of the shaft spillway reduce the flow discharge considerably. The common solution for avoiding air-entrainment and swirl is to provide sufficient submergence to the intake. If the required approach flow conditions cannot be met to avoid swirl and air entrainment, other approaches for preventing vortices at water intakes are considered. Anti-vortex devices are used as means to reduce the vortex flow strength. The most economic and common measure to reduce the air-entrainment and swirling flow strength, is optimized shape of inlet e.g. by installing a circular Piano-Key (PK) inlet over the pipe intake. In this study, the flow field around the shaft spillways using PK inlet were investigated numerically. PK inlet due to its special configuration reduces the swirling flow strength and has a significant effect on increasing the discharge coefficient of shaft spillway. The flow field around the structure and inside the vertical shaft spillway was modeled using FLUENT 6.3.26 software. For this purpose, the governing differential equations of motion in a cylindrical coordinate system were solved using Volume of Fluids (VoF) method. Air-water two phase flow was applied on free water surface and standard “k-e” turbulence model was used. Three different flow regimes including; “free weir flow”, “orifice control flow” and “pressurized flow” were considered in modeling. The model consists of a cylindrical tank of 2 m in diameter and 1 m in height. A vertical shaft of 0.126 m in diameter was installed at the center of the tank floor equipped with the PK inlet over it. Accordingly, the effects of the PK inlet’s geometries, including the inlet length, height and angle on hydraulics flow through the shaft and the flow discharge coefficient were investigated. The effects of bend on bottom outlet were also studied. The flow characteristics such as variations of pressure and 3-D flow velocities have been calculated. Results show that, PK inlets increase the flow discharge considerably compared to a simple shaft or even morning-glory spillways. Finally, a best geometry of PK inlet was suggested to achieve the maximum efficiency of vertical shaft spillways. Keywords : Vertical shaft spillway, Swirling flow, VoF method, PK inlet