Vena contracta

Vena contracta is a term used in fluid dynamics and medical imaging to describe the phenomenon that occurs in a fluid flow when it passes through a constricted area. Specifically, it refers to the point of minimum cross-sectional area downstream from a restriction, such as a valve or a stenosis in a blood vessel. In the context of blood flow, for example, when blood passes through a narrowed area in a vessel, the velocity of the blood increases as it enters the constriction.