Mach number, definition

By measuring the total and static pressure and using Equation (3-14), the Mach number can be calculated. Using Equation (3-12), the static temperature can be computed, since the total temperature can be measured. Finally, using the definition of Mach number, the velocity of the gas stream can be calculated. 

But, as shown previously, RkT IM is the square of the speed of sound at state 1, or Cl, so the left side is (1/,/c,). The ratio V/c is called the Mach number M in honor of the Austrian physicist Ernst Mach. This ratio plays a crucial role in the study of high-velocity gas flows (and is widely reported in the press describing the speed of supersonic aircraft). It is the ratio of the local flow velocity to the local speed of sound. For subsonic flows M is less than 1 for sonic flows it equals 1 for supersonic flows it is greater than 1. Making this definition, we can rearrange Eq. 8.15 to... 

In view of the fact that the sampling conditions are somewhat less than ideal, time-dependent signals obtained for radicals must be viewed with some caution. The time dependence of the major components, however, should be unaffected by the low Mach number flow through the sampling cone. Subsequent experiments with the 110 cone should provide much more definitive information on radical relative mole fractions, temperature, and perhaps also absolute mole fractions of a number of components. 

In these equations, the q subscript denotes source conditions, M is the Mach number, 7 is the ratio of specific heats (X= 5/3 for a rare gas), a is the local speed of sound, and v is the flow velocity. The definition of a is... 

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