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In fluid mechanics the term static pressure has several uses: * In the design and operation of aircraft, ''static pressure'' is the air pressure in the aircraft’s static pressure system. * In fluid dynamics, many authors use the term ''static pressure'' in preference to just ''pressure'' to avoid ambiguity. Often however, the word ‘static’ may be dropped and in that usage pressure is the same as static pressure at a nominated point in a fluid. * The term ''static pressure'' is also used by some authors in fluid statics. == Static pressure in design and operation of aircraft == An aircraft’s altimeter is operated by the static pressure system. An aircraft’s airspeed indicator is operated by the static pressure system and the pitot pressure system.〔Lombardo, D.A., ''Aircraft Systems'', 2nd edition – chapter 2〕 The static pressure system is open to the exterior of the aircraft to sense the pressure of the atmosphere at the altitude at which the aircraft is flying. This small opening is called the static port. In flight the air pressure is slightly different at different positions around the exterior of the aircraft. The aircraft designer must select the position of the static port carefully. There is no position on the exterior of an aircraft at which the air pressure, for all angles of attack, is identical to the atmospheric pressure at the altitude at which the aircraft is flying.〔"It is virtually impossible to find a position where the static pressure is always exactly the same as the pressure in the free airstream away from the aircraft". Kermode, A.C., ''Mechanics of Flight'', 10th edition – page 65〕 The difference in pressure causes a small error in the altitude indicated on the altimeter, and the airspeed indicated on the airspeed indicator. This error in indicated altitude and airspeed is called position error.〔Kermode, A.C., ''Mechanics of Flight'', 10th Edition – page 65〕〔"Of these errors the error in detection of static pressure is generally the most serious and has the special name, ''position error''." Dommasch, D.O., Sherby, S.S., and Connolly, T.F. (1967) ''Airplane Aerodynamics'', 4th edition – page 51, Pitman Publishing Corp., New York〕 When selecting the position for the static port, the aircraft designer’s objective is to ensure the pressure in the aircraft’s static pressure system is as close as possible to the atmospheric pressure at the altitude at which the aircraft is flying, across the operating range of weight and airspeed. Many authors describe the atmospheric pressure at the altitude at which the aircraft is flying as the ''freestream static pressure''. At least one author takes a different approach in order to avoid a need for the expression ''freestream static pressure''. Gracey has written "The static pressure is the atmospheric pressure at the flight level of the aircraft".〔Gracey, William, (''Measurement of aircraft speed and altitude'' ) NASA, RP-1046, page 1〕〔Gracey, William, ''Measurement of Aircraft Speed and Altitude'', page 1〕 Gracey then refers to the air pressure at any point close to the aircraft as the ''local static pressure''. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Static pressure」の詳細全文を読む スポンサード リンク
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