What is a Venturi Meter?

A Venturi meter is a high-precision flow measurement device used in fluid mechanics to determine the discharge or flow rate of a fluid passing through a pipe. It works on the principle of Bernoulli's equation. The device consists of three main parts: a converging section, a cylindrical throat, and a diverging section. As fluid enters the throat, its velocity increases while its pressure decreases. By measuring the pressure difference between the inlet and the throat, the flow rate can be calculated with extreme accuracy.

How the Venturi Meter Calculator Works

This calculator uses the theoretical discharge formula adjusted by a coefficient of discharge (Cd). To use the tool, you need the following parameters:

• Inlet Diameter (D1): The diameter of the main pipe where the fluid enters.
• Throat Diameter (D2): The narrowed portion of the meter.
• Differential Head (h): The height difference of the liquid column (typically measured by a manometer).
• Coefficient of Discharge (Cd): A dimensionless number (usually between 0.95 and 0.99) that accounts for energy losses due to friction.

Venturi Meter Formula

The flow rate (Q) is calculated using the following equation:

Q = Cd × [(A1 × A2) / √(A1² - A2²)] × √(2gh)

Where A1 and A2 are the cross-sectional areas of the inlet and throat respectively, g is the acceleration due to gravity (9.81 m/s²), and h is the differential head.

Frequently Asked Questions

Why is the Venturi meter preferred over an Orifice meter?
While more expensive, the Venturi meter has a much lower pressure loss because the diverging section allows the fluid to recover most of its pressure energy. It is also less prone to clogging.

What is a typical Cd value?
For a well-manufactured Venturi meter, the coefficient of discharge usually ranges from 0.96 to 0.99, indicating very high efficiency.