Introduction to Food Engineering

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Fluid Flow Measurements

Learning Outcomes

At the end of this module, you will be able to:

  1. distinguish among different terms used to describe pressure
  2. describe how a U-tube manometer is used in pressure measurements
  3. describe the use of a Pitot tube to measure fluid velocity

In this module, we will learn how to measure fluid flow. Typically, we measure changes in pressure and then express those changes in terms of fluid velocity, volumetric flow rate, or mass flow rate. In the first video, you will learn various terms used in describing pressure in fluids either when they are stationary or moving, such as static pressure, dynamic pressure, stagnation pressure, and total pressure.

In the next video, you will learn how to use a U-tube manometer to determine the pressure in a fluid at any desired location.

Next, you will learn about a widely used sensor in fluid flow measurements, namely, a Pitot tube. A Pitot-tube, along with a manometer, allows one to obtain an accurate measurement of fluid pressure. In the next video, you will learn the basic construction of a Pitot tube and its use in measuring total pressure and static pressure.

We will now consider mathematical expressions for different pressures measured with a Pitot tube.

In the next video, you will learn how to develop a mathematical expression to determine fluid velocity when using a Pitot tube along with a U-tube manometer.

Next, we consider a numerical example to illustrate the use of a Pitot tube and a U-tube manometer in measuring fluid velocity.


In this video, you learned various terms used in pressure measurements relevant to static or moving fluid. You learned how to obtain a pressure difference between two locations using a U-tube manometer. Pitot tube is a widely used sensor to measure fluid velocity. You learned how a U-tube manometer and a Pitot tube are used together in fluid flow measurements.