Mechanical simulations are performed to compare the hydraulic behavior of centrifugal and regenerative pumps using an open-source CFD software. The pump geometries are prepared through CAD cleaning and repairing procedures, while finite volume methods are employed to solve the flow field. The results highlight significant differences in the internal flow patterns: the regenerative pump exhibits complex recirculation phenomena, whereas the centrifugal pump shows a smoother and more uniform radial flow. These findings provide insight into the distinct operating principles of the two pump technologies.