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FLOW / 005
Mach Number Calculator
Estimate Mach number or velocity for an ideal gas using the local speed of sound. Useful when deciding whether compressibility needs explicit attention in a CFD setup.
Compressible flowIdeal gasSpeed of sound
INTERPRETATION
Mach number is a compressibility indicator—not a complete model-selection rule.
For many engineering gas flows, Mach number below roughly 0.3 is a common starting indication that density changes caused purely by velocity may be modest. Thermal density changes, pressure ratios, buoyancy or other physics can still require variable density.
01
Use local conditions. Speed of sound depends on local thermodynamic state.
02
Check the whole domain. A low inlet Mach number does not prevent acceleration to transonic conditions elsewhere.
03
Separate compressibility from density variation. Heating and buoyancy can matter even at low Mach.