16.4 : Static, Stagnation, Dynamic and Total Pressure

The concept of static, stagnation, dynamic, and total pressure is fundamental in fluid dynamics, often explained using Bernoulli's equation:

Here, p is static pressure,1/2⍴V² is dynamic pressure, γz is hydrostatic pressure or potential energy pressure, and p_T is total pressure, constant along a streamline for incompressible flows.

1. Static Pressure (p): This is the pressure exerted by a fluid at rest or as if flowing fluid is brought to rest in the direction of motion. It is measured using a probe inserted into the flow or by a piezometer tube.

2. Dynamic Pressure (1/2⍴V²): It represents the pressure rise due to the fluid's velocity. It can be interpreted as the kinetic energy per unit volume of the fluid.

3. Stagnation Pressure (p_s): It is the sum of static and dynamic pressures at a stagnation point, where the velocity of the fluid becomes zero:

4. Total Pressure (p_T): This is the sum of static, dynamic, and hydrostatic pressures. Along a streamline:

A Pitot-static tube measures stagnation pressure (p_s) and static pressure (p). By calculating the difference, the velocity of the fluid can be determined:

In applications, such as measuring airspeed in aviation, ensuring accurate alignment and placement of the Pitot-static tube is critical. Misalignment or blockage can lead to erroneous readings, impacting operational safety.