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'Stagnation pressure' is the pressure at a stagnation point in a fluid flow, where the kinetic energy is converted into pressure energy. It is the sum of the Dynamic pressure and Static pressure at the stagnation point. ^[1]
Pitot tubes are used to measure stagnation (or total) pressure. A combined pitot/static tube is used on aircraft to determine flight speed. Stagnation quantities (e.g. stagnation temperature, stagnation pressure) are also frequently used in jet engine performance calculations.

Contents

Definition

Thermal Definition

See also

References

External links

Definition

The definition for Stagnation pressure can be derived from the Bernoulli Equation^[2]


Stagnation (Total) Pressure = Dynamic Pressure + Static Pressure
or

ho v^2 + P_{static}
{|
|-
| where: || $P\_\{stagnation\}$ || is the stagnation (or total) pressure in Pascals
|-
| || $$
ho || is the fluid density in kg/m³
|-
| || $v$ || is the fluid velocity relative to the stagnation point before it becomes influenced by the object which causes stagnation in ms^-1
|-
| || $P\_\{static\}$ || is the static fluid pressure away from the influence of the moving fluid in Pascals
|}

Thermal Definition

It is the pressure a fluid retains when brought to rest isentropically from mach number M.

ight)^{rac{gamma}{gamma-1}},
or, assuming an isentropic process, the stagnation pressure can be calculated from the ratio of stagnation temperature to static temperature:

ight)^{rac{gamma}{gamma-1}},
where:
$p\_t\; =,$ stagnation (or total) pressure
$p\; =,$ static pressure
$T\_t\; =,$ stagnation (or total) temperature in kelvin
$T\; =,$ static temperature in kelvin
$gamma\; =,$ ratio of specific heats
The above derivation holds only for the case when the fluid is assumed to be calorically perfect. For such fluids, specific heats and $gamma$ are assumed to be constant and invariant with temperature (See also, a thermally perfect fluid).

See also

★ Stagnation point

★ Dynamic Pressure

★ Static Pressure

★ Pitot tube

References

1. Stagnation Pressure at Eric Weisstein's World of Physics (Wolfram Research)
2. Equation 4, Bernoulli Equation - The Engineering Toolbox

External links