static pressure

In fluid mechanics the term static pressure refers to a term in Bernoulli's equation written as static pressure + dynamic pressure = total pressure. Since pressure measurements at any single point in a fluid always give the static pressure value, the 'static' is often dropped. In the design and operation of aircraft, static pressure is the air pressure in the aircraft's static pressure system.

In fluid mechanics the term static pressure refers to a term in Bernoulli's equation written as static pressure + dynamic pressure = total pressure. Since pressure measurements at any single point in a fluid always give the static pressure value, the 'static' is often dropped. In the design and operation of aircraft, static pressure is the air pressure in the aircraft's static pressure system. P + \frac{1}{2} \rho v^2 = P_0, where: P\; is static pressure, \frac{1}{2} \rho v^2 is dynamic pressure, usually denoted by q\; , \rho\, is the density of the fluid, v\, is the flow velocity, and P_0\; is total pressure which is constant along any streamline. It is also known as the stagnation pressure. Every point in a steadily flowing fluid, regardless of the fluid speed at that point, has its own static pressure P , dynamic pressure q , and total pressure P_0 . Static pressure and dynamic pressure are likely to vary significantly throughout the fluid but total pressure is constant along each streamline. In irrotational flow, total pressure is the same on all streamlines and is therefore constant throughout the flow. The simplified form of Bernoulli's equation can be summarised in the following memorable word equation: static pressure + dynamic pressure = total pressure. This simplified form of Bernoulli's equation is fundamental to an understanding of the design and operation of ships, low speed aircraft, and airspeed indicators for low speed aircraft – that is aircraft whose maximum speed will be less than about 30% of the speed of sound. As a consequence of the widespread understanding of the term static pressure in relation to Bernoulli's equation, many authors in the field of fluid dynamics also use static pressure rather than pressure in applications not directly related to Bernoulli's equation. The British Standards Institution, in its Standard Glossary of Aeronautical Terms, gives the following definition: 4412 Static pressure The pressure at a point on a body moving with the fluid.

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