In fluid dynamics dynamic pressure depends on density and velocity of the fluid.
It is defined by the following equation (with q standing for dynamic pressure or "velocity pressure"):
where (using SI units):
Dynamic pressure
Measurement
To measure the dynamic pressure, the static pressure must be subtracted from the pressure at the stagnation point (total pressure) according to the above formula. This can be done by measuring the static pressure separately, followed by a calculated subtraction. Another possibility is to use a differential pressure sensor, where the difference is formed in a physical way: the sensor is supplied with hoses with the local pressure at the stagnation point and the static pressure at a surface perpendicular to the incident flow.
The stagnation point at which the measurement is taken should be exposed to the air flow as unobstructed as possible. For this reason, a Pitot tube is used in aircraft, the opening of which protrudes in front of the nose or the tail unit. The Prandtl probe is a special design in which the openings for the pressure measurements are positioned in such a way that the measurement error is as small as possible when the airflow is oblique.
See also
- Resting pressure
- Bernoulli equation
- Venturi nozzle
- Max Q (space physics), point of maximum dynamic pressure