In a venturi tube, where does the greatest restriction occur?

In a venturi tube, the greatest restriction occurs at the throat. The throat is the narrowest section of the Venturi tube, which is designed to create a specific pressure drop as fluid flows through it. When the fluid enters the venturi tube, it encounters a gradually narrowing section until it reaches the throat. At this point, due to the conservation of mass principle, the velocity of the fluid increases while its pressure decreases, leading to an increase in kinetic energy. This behavior is key to the design and function of flow measurement systems and fluid dynamics applications.

The other sections of the venturi tube, such as the inlet and the expansion section, do not exhibit the same level of restriction as the throat. The inlet allows fluid to enter smoothly, while the expansion section lets the fluid exit, transitioning back to a larger diameter. These sections are important for the overall operation of the venturi tube, but they do not provide the critical narrowing necessary for generating the pressure differential characteristic of flow through the throat.