We introduce an innovative lumped-parameter model of the aortic valve, designed to efficiently simulate the impact of valve dynamics on blood flow. Our reduced model includes the elastic effects associated with the leaflets’ curvature and the stress exchanged with the blood flow. The introduction of a lumped-parameter model based on momentum balance entails an easier calibration of the model parameters: Phenomenological-based models, on the other hand, typically have numerous parameters. This model is coupled to 3D Navier–Stokes equations describing the blood flow, where the moving valve leaflets are immersed in the fluid domain by a resistive method. A stabilized finite element method with a BDF time scheme is adopted for the discretization of the coupled problem, and the computational results show the suitability of the system in representing the leaflet motion, the blood flow in the ascending aorta, and the pressure jump across the leaflets. Both physiological and stenotic configurations are investigated, and we analyze the effects of different treatments for the leaflet velocity on the blood flow.