Mach number regimes
From CFD-Wiki
Compressible flows are commonly divided into different regimes based on the free-stream Mach number according to the following table:
Flow regime | Mach number range |
Incompressible flow | 0.0 - 0.3 |
Subsonic flow | 0.3 - 0.8 |
Transonic flow | 0.8 - 1.2 |
Supersonic flow | 1.2 - 5.0 |
Hypersonic flow | > 5.0 |