Measurement between these two pressures is what gives us dynamic pressure, which can be used to calculate airspeed. the side hole measures what’s called static pressure. The front hole is placed in the airstream, helping to measure what is known as stagnation pressure. A pitot tube is a slender tube, having two holes on it. The device was modified to its modern form in the mid-19 th century by a French scientist Henry Darcy. It was invented by Henri Pitot who was a French engineer in the 18 th century. 9 Advantages and disadvantages of a pitot tubeĪ pitot tube is a flow measurement instrument for measuring the velocity (speed) of a flowing fluid.
#Measuring static vs stagnation pressure using a pitot tube how to
Dynamic pressure is given by the expression, ½ ρV2. The symbol, P, is often used for static pressure. Static Pressue, Stagnation Pressue and Dynamic Pressure - Relationships Its measurement is illustrated with the third U-tube in the diagram at the left. It can also be interpreted as the pressure created by reducing the kinetic energy to zero. Stagnation pressure (also called total pressure) measurement is illustrated with the second U-tube manometer in the diagram at the left.ĭynamic pressure (also called velocity pressure) is a measure of the amount that the stagnation pressure exceeds static pressure at a point in a fluid.
It is measured through a flat opening that is perpendicular to the direction of fluid flow and facing into the fluid flow. Stagnation pressure is also a measure of the amount that fluid pressure exceeds local atmospheric pressure, but it includes the effect of the fluid velocity converted to pressure. Static pressure measurement is illustrated with the first U-tube manometer in the diagram at the left. It is measured through a flat opening that is parallel with the fluid flow. It’s a measure of the amount that fluid pressure exceeds local atmospheric pressure. Static pressure is what is commonly called simply the pressure of the fluid. Understanding of the terms, static pressure, stagnation pressure and dynamic pressure is very helpful in the explanation of pitot tubes, so they are being defined in this section. Static Pressure, Stagnation Pressure and Dynamic Pressure - Definitions Pitot tubes (also called pitot-static tubes) are used, for example, to make airflow measurements in HVAC applications and for aircraft airspeed measurements. This is a convenient, inexpensive method for measuring velocity at a point in a flowing fluid. Pitot tubes are used in a variety of applications for measuring fluid velocity.