The comparative numerical analysis of the butterfly valve is performed to simulate the fluid flow inside the pipe. In this study, the performance of the single-disc butterfly valve flow is investigated in the opening process. The flow separation for the turbulent case is also examined to observe the velocity and pressure distributions since the unsteady flow can be understood well with an examination of the velocity and pressure changes. The formations of the vortexes are considered. In addition, an optimization study is done to decrease the operational coefficient values. In the result of the study, the characteristic parameters of the conventional and optimized valves are compared including, flow coefficient; drag coefficients, and dynamic torque. The changes of the characteristic parameters at different opening angles are demonstrated as tables and graphs to evaluate the performance of the valves.