Stagnation and Sonic Properties
- The stagnation properties at a point are defined as those which are to be obtained if the local flow were imagined to cease to zero velocity isentropically. As we will see in the later part of the text, stagnation values are useful reference conditions in a compressible flow.
Let us denote stagnation properties by subscript zero. Suppose the properties of a flow (such as T, p , ρ etc.) are known at a point, the stangation enthalpy is, thus, defined as
where h is flow enthalpy and V is flow velocity.
- For a perfect gas , this yields,
which defines the Stagnation Temperatur 
Now,  can be expressed as
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(40.2) |
If we know the local temperature (T) and Mach number (Ma) , we can find out the stagnation temperature T0 .
- Consequently, isentropic(adiabatic) relations can be used to obtain stagnation pressure and stagnation density as
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(40.3) |
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(40.4) |
Values of  and  as a function of Mach number can be generated using the above relationships and the tabulated results are known as Isentropic Table . Interested readers are suggested to refer the following books
1. J.Spruk, Fluid Mechanics, Springer, Heidelberg , NewYork, 1997
2.
K.Muradidhar and G.Biswas, Advanced Engineering Fluid Mechanics, Second Edition, Narosa, 2005
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