Stagnation Pressure

on . Posted in Classical Mechanics

Stagnation pressure, abbreviated as \(p_s\), also called total pressure or pitot pressure, is a concept in fluid dynamics that represents the sum of static pressure and dynamic pressure at a specific point in a flowing fluid.  It's called stagnation pressure because it is the pressure that would be measured if the fluid were brought to rest or stagnated at that point.  Stagnation pressure accounts for both the static pressure, which is the pressure exerted by the fluid due to its molecular collisions, and the dynamic pressure, which is the pressure resulting from the kinetic energy of the fluid's motion. It is a useful quantity in analyzing fluid flows, particularly when considering the energy content of the fluid.

The stagnation pressure can be measured using a device called a pitot tube, which is commonly used in aerodynamics and fluid dynamics. The pitot tube has two openings, one facing the flow direction to measure the stagnation or total pressure, and another opening perpendicular to the flow to measure the static pressure.  By subtracting the static pressure from the stagnation pressure, the dynamic pressure can be determined.

Stagnation pressure is a valuable parameter in various applications, such as aerodynamics, gas dynamics, and fluid flow analysis.  It is used to calculate quantities like total head, total temperature, and total energy in fluid systems.


Stagnation Pressure formula

\( p_s =  \frac{ 1 }{ 2 } \; \rho\; v^2  + SP  \) 
Symbol English Metric
\( p_s \) = stagnation pressure \(lbf \;/\; in^2\)  \(Pa\) 
\( \rho \)   (Greek symbol rho) = density of fluid \(lbm \;/\;ft^3\) \(kg \;/\; m^3\)
\( v \) = velocity of fluid \(ft \;/\; sec\) \(m \;/\; s\)
\( SP \) = static pressure \(ft^3 \;/\; min\) \(m^3 \;/\; min\)


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Tags: Pressure