# Back pressure

The dynamic pressure is the increase in pressure at the stagnation point of a body in flow compared to the static pressure of the fluid : ${\ displaystyle p _ {\ mathrm {stau}}}$ ${\ displaystyle p_ {0}}$ {\ displaystyle {\ begin {aligned} p _ {\ mathrm {stau}} & = p_ {t} -p_ {0} \\ & = {\ frac {\ rho} {2}} \ cdot v ^ {2} \ end {aligned}}} With

• the total pressure at the stagnation point${\ displaystyle p_ {t}}$ • the density of the flowing medium${\ displaystyle \ rho}$ • the flow velocity .${\ displaystyle v}$ The dynamic pressure thus corresponds to the dynamic pressure .

The velocity in relation to the fluid can be determined with the help of the dynamic pressure.

## Measurement

To measure the dynamic pressure, according to the above Formula the static pressure can be subtracted from the pressure at the stagnation point (total or total pressure). This can be done by a separate measurement of the static pressure, followed by a computational subtraction. Another possibility is to use a differential pressure sensor in which the difference is formed in a physical way: the sensor is supplied with the local pressure at the stagnation point and the static pressure on a surface perpendicular to the flow to the sensor.

The stagnation point at which the measurements are made should be flown against as undisturbed as possible. For this reason, a pitot tube is used in aircraft , the opening of which protrudes in front of the nose or tail unit . The Prandtl probe is a special design in which the openings for the pressure measurements are placed in such a way that the smallest possible measurement error results with an inclined flow .