Why divergent cone in venturi meter is longer than convergent cone?

The divergent cone in a Venturi meter is longer than the convergent cone to ensure a gradual expansion of the fluid flow. This gradual expansion minimizes turbulence and pressure loss, allowing for more accurate measurements of flow rates. A longer divergent section helps to maintain smoother flow patterns, which is essential for the Venturi effect to function effectively. In contrast, a rapid expansion would lead to flow separation and energy losses.