View source for Mach number

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One of the basic criteria of aerodynamic similarity when the [[viscosity]] of the gas cannot be neglected. Mach's number $M=v/a$ is the ratio of the velocity of the gas flow and the velocity of sound at the same point of the flow (or the ratio of the velocity of a body in the gas and the velocity of sound in this medium). The number was called thus to honour E. Mach.

====References====
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<TR><TD valign="top">[a1]</TD> <TD valign="top">  L. Howarth (ed.) , ''Modern development in fluid dynamics. High speed flow'' , '''1–2''' , Oxford Univ. Press  (1953)</TD></TR>
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