Week 3 - Pitot tube

Literature Review of Pitot tube

Pitot tube is instrument used to measure velocity of fluid flow at a point, based on measurement of differential pressure between Stagnation and static pressure simultaneously.

Working

Pitot tube is basically a thin tube with holes on it, the hole on front of tube that is tip of tube is placed directly in airstream, pressure is created as fluid flows through a tube, there is no outlet in tube so, fluid comes to rest this is Stagnation pressure. Whereas the side hole measures static pressure created from moving fluid. From these two pressure we obtain dynamic pressure by calculating the difference between them. Dynamic pressure can be used to determine velocity of fluid flow in aircrafts.

Purpose

Aircrafts travels with definite operating envelope, if it travels below operating envelope chances are that aircraft can stall (sudden reduction in lift) is dangerous as pilot won’t be able control aircraft. If it exceeds the operating envelope it may cause structural damage which can also be dangerous to fly an aircraft.

Application

Used to measure aircrafts airspeed as speedometers, measure velocity of air and fluid in industrial application.

Advantages

Small

Low cost

Ease in installation to any device

Does not contain any moving part

Disadvantages

Low range and Accuracy

Disrupt the reading if foreign particle clogs the tube

Relation between Stagnation and Static pressure is:

Stagnation Pressure = Dynamic Pressure + Static Pressure

P_Stagnation = ½*ρ* V² + P_Static

Where :

P_Stagnation = Stagnation Pressure of fluid

P_Static = Static Pressure of fluid

ρ= Density of fluid

V = Velocity of fluid