LESSON 20. VENTURIMETER, ORIFICEMETER AND NOZZLE, SIPHON FLOWRATE MEASUREMENT

venturimeter

  • The Venturi meter is a device for measuring discharge in a pipe.

  • It is a rapidly converging section which increases the velocity of flow and hence reduces the pressure.

  • It then returns to the original dimensions of the pipe by a gently diverging ‘diffuser’ section.

Module 12,13 Lesson 20 VENTURIMETER

Apply Bernoulli along the streamline from point 1 to point 2

Module 12,13 Lesson 20 Venturimeter 1.1

By continuity

Module 12,13 Lesson 20 Venturimeter 1.2

Module 12,13 Lesson 20 Venturimeter 1.3

Substituting and rearranging gives

Module 12,13 Lesson 20 Venturimeter 1.4

Module 12,13 Lesson 20 Venturimeter 1.5

Module 12,13 Lesson 20 Venturimeter 1.6

The theoretical (ideal) discharge is u×A.

Actual discharge takes into account the losses due to friction, we include a coefficient of discharge (Cd ≈ 0.9)

Module 12,13 Lesson 20 Venturimeter 1.7

Module 12,13 Lesson 20 Venturimeter 1.8

Module 12,13 Lesson 20 Venturimeter 1.9

In terms of the manometer readings

Module 12,13 Lesson 20 Venturimeter 1.10

Module 12,13 Lesson 20 Venturimeter 1.11

Giving

Module 12,13 Lesson 20 Venturimeter 1.12

This expression does not include any elevation terms. (z1 or z2) When used with a manometer

The Venturimeter can be used without knowing its angle.

Last modified: Monday, 16 September 2013, 6:55 AM