The Mach number is a dimensionless unit used to represent the speed of an object moving through a fluid, such as air or gas. In subsonic flows (M < 1), the compressibility effects are typically small, and the static pressure changes are relatively gradual with increasing Mach number. Mathematically, it is expressed as:
where:
- is the Mach number,
- is the dynamic pressure,
- is the heat capacity ratio,
- is the static pressure.