where M^{*} is the characteristic Mach number ( No unit)

M is the Mach Number ( No unit)

γ is the ratio of specific heat (No unit)

M^{∗} = V/a^{*} = V/(γ×R×T^{*} )^0.5

where V is the local flow velocity (m/s)

T^{∗ } is the temperature at sonic condition (K)

R is the specific gas constant (0.287 KJ/kgK)