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In compressible fluid dynamics, impact pressure (dynamic pressure) is the difference between total pressure (also known as pitot pressure or stagnation pressure) and static pressure. [ 1 ] [ 2 ] In aerodynamics notation, this quantity is denoted as q c {\displaystyle q_{c}} or Q c {\displaystyle Q_{c}} .
Dynamic pressure is one of the terms of Bernoulli's equation, which can be derived from the conservation of energy for a fluid in motion. [1] At a stagnation point the dynamic pressure is equal to the difference between the stagnation pressure and the static pressure, so the dynamic pressure in a flow field can be measured at a stagnation point ...
where a 0 is 1,225 km/h (661.45 kn) (the standard speed of sound at 15 °C), M is the Mach number, P is static pressure, and P 0 is standard sea level pressure (1013.25 hPa). Combining the above with the expression for Mach number gives EAS as a function of impact pressure and static pressure (valid for subsonic flow):
These formulae can then be used to calibrate an airspeed indicator when impact pressure is measured using a water manometer or accurate pressure gauge. If using a water manometer to measure millimeters of water the reference pressure ( P 0 {\\displaystyle P_{0}} ) may be entered as 10333 mm H 2 O {\\displaystyle H_{2}O} .
In fluid dynamics, stagnation pressure, also referred to as total pressure, is what the pressure would be if all the kinetic energy of the fluid were to be converted into pressure in a reversable manner. [1]: § 3.2 ; it is defined as the sum of the free-stream static pressure and the free-stream dynamic pressure. [2]
Bernoulli's principle is a key concept in fluid dynamics that relates pressure, density, speed and height. Bernoulli's principle states that an increase in the speed of a parcel of fluid occurs simultaneously with a decrease in either the pressure or the height above a datum. [1]:
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In hypersonic flow, the pressure coefficient can be accurately calculated for a vehicle using Newton's corpuscular theory of fluid motion, which is inaccurate for low-speed flow and relies on three assumptions: [5] The flow can be modeled as a stream of particles in rectilinear motion; Upon impact with a surface, all normal momentum is lost