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The pressure coefficient is a dimensionless number which describes the relative pressures throughout a flow field in fluid dynamics. The pressure coefficient is used in aerodynamics and hydrodynamics. Every point in a fluid flow field has its own unique pressure coefficient, . In many situations in aerodynamics and hydrodynamics, the pressure coefficient at a point near a body is independent of body size. Consequently an engineering model can be tested in a wind tunnel or water tunnel, pressure coefficients can be determined at critical locations around the model, and these pressure coefficients can be used with confidence to predict the fluid pressure at those critical locations around a full-size aircraft or boat. ==Incompressible flow== (詳細はpressure at the point at which pressure coefficient is being evaluated : is the pressure in the freestream (i.e. remote from any disturbance) : is the freestream fluid density (Air at sea level and 15 °C is 1.225 ) : is the freestream velocity of the fluid, or the velocity of the body through the fluid Using Bernoulli's Equation, the pressure coefficient can be further simplified for incompressible, lossless, and steady flow:〔Anderson, John D. ''Fundamentals of Aerodynamics''. 4th ed. New York: McGraw Hill, 2007. 219.〕 : where V is the velocity of the fluid at the point at which pressure coefficient is being evaluated. This relationship is also valid for the flow of compressible fluids where variations in speed and pressure are sufficiently small that variations in fluid density can be ignored. This is a reasonable assumption when the Mach Number is less than about 0.3. * of zero indicates the pressure is the same as the free stream pressure. * of one indicates the pressure is stagnation pressure and the point is a stagnation point. * of minus one is significant in the design of gliders because this indicates a perfect location for a "Total energy" port for supply of signal pressure to the Variometer, a special Vertical Speed Indicator which reacts to vertical movements of the atmosphere but does not react to vertical maneuvering of the glider. In the fluid flow field around a body there will be points having positive pressure coefficients up to one, and negative pressure coefficients including coefficients less than minus one, but nowhere will the coefficient exceed plus one because the highest pressure that can be achieved is the stagnation 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「pressure coefficient」の詳細全文を読む スポンサード リンク
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