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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 ...
[1]: § 3.2 ; it is defined as the sum of the free-stream static pressure and the free-stream dynamic pressure. [2] The Bernoulli equation applicable to incompressible flow shows that the stagnation pressure is equal to the dynamic pressure and static pressure combined. [1]: § 3.5 In compressible flows, stagnation pressure is also equal to ...
The above equations suggest there is a flow speed at which pressure is zero, and at even higher speeds the pressure is negative. Most often, gases and liquids are not capable of negative absolute pressure, or even zero pressure, so clearly Bernoulli's equation ceases to be valid before zero pressure is reached.
For this reason flux represents physically a flow per unit area. ... Bernoulli's equation: p constant is the total pressure at a point on a streamline + ...
The Bernoulli equation applicable to incompressible flow shows that the stagnation pressure is equal to the dynamic pressure and static pressure combined. [1]: § 3.5 In compressible flows, stagnation pressure is also equal to total pressure as well, provided that the fluid entering the stagnation point is brought to rest isentropically.
In irrotational flow, total pressure is the same on all streamlines and is therefore constant throughout the flow. [5] The simplified form of Bernoulli's equation can be summarised in the following memorable word equation: [6] [7] [8] static pressure + dynamic pressure = total pressure.
As a rough guide, compressible effects can be ignored at Mach numbers below approximately 0.3. For liquids, whether the incompressible assumption is valid depends on the fluid properties (specifically the critical pressure and temperature of the fluid) and the flow conditions (how close to the critical pressure the actual flow pressure becomes).
The dynamic pressure at both the upstream and the downstream stagnation point has a value of 1 / 2 ρU 2. This value is needed to decelerate the free stream flow of speed U to zero speed at both these points. This symmetry arises only because the flow is completely frictionless.