Abstract: Valves are one of the main components of fluid control devices in applications such as oil and gas machinery. They play an important role in the efficiency of these systems in terms of energy and performance. Therefore, understanding the flow characteristics and behavior in valves is vitally important in the design and optimization of such systems. A Computational Fluid Dynamics (CFD) simulation is performed using an in-house code for ball and conical head poppet valves. The flow is turbulent, incompressible and unsteady. In order to obtain good and converged results, the RNG-k-ε turbulence model is applied for this purpose. Simulations apply a velocity inlet and pressure outlet. The effect of different gap sizes and the shape of the valve are investigated. The results are compared with each other and with available experimental data. They also show good agreement with the works found in the literature. It was concluded that the shape of the valve has a dominant effect on flow behavior, while recirculation of the flow and a high-velocity region in the gap are the main characteristics of the flow in valve systems.